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IFR Alternate Airports: The 1-2-3 Rule, 600-2 vs. 800-2, Why LPV Doesn't Count, and the GPS Rules

Dec 23, 2025
17 min read

Updated: 5 days ago

When flying under Instrument Flight Rules, planning for the destination alone is not enough. Weather changes, approaches go NOTAMed out, and the forecast you briefed two hours ago may not be the weather you arrive to. To manage that risk, the regulations require you to plan an alternate airport under certain conditions — and the rules for when you need one and which airports qualify have more structure than most pilots carry around. The 1-2-3 rule is only the trigger. Behind it sit two conditions that must both be met to skip the alternate, a set of standard and non-standard alternate minimums, a widely misunderstood rule about GPS approaches (LPV does not get you 600-2), and a fuel requirement that applies whether or not you ever divert.


This post covers IFR alternate requirements in practical depth: what an alternate is for, the two conditions for not needing one (the 1-2-3 rule and the Part 97 approach requirement), how to read the TAF including TEMPO and PROB groups, the standard alternate minimums and the GPS/LPV rules done correctly, non-standard minimums and the ⧊A and NA symbols, the alternate-minimums-versus-landing-minimums distinction, fuel, takeoff alternates, and the checkride questions with answers.



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What an Alternate Airport Is

An alternate airport is a secondary airport listed in an IFR flight plan that you can divert to if landing at the intended destination becomes unsafe or impractical.


Alternates exist to ensure:

  • A safe landing option if the destination weather deteriorates below minimums

  • Compliance with fuel reserve requirements (you must carry fuel to reach it)

  • Reduced pressure to attempt an approach you shouldn't — you always have somewhere else to go

  • A planned, briefed Plan B rather than an improvised one


The planning-vs-reality distinction:

  • The filed alternate is a PLANNING requirement — it proves you have the fuel and a legal place to go

  • In flight, you may divert ANYWHERE suitable; you are not bound to the filed alternate

  • If a closer or better airport is above minimums when you need it, go there

  • The filed alternate is the floor of your options, not the ceiling


The Regulation: 14 CFR 91.169

The alternate requirement lives in 91.169, and it has two parts pilots must keep straight.


91.169(b) — when an alternate is required:

  • Unless otherwise authorized by ATC, an IFR flight plan must include an alternate airport — UNLESS two conditions are both met (next section)

  • The default is: file an alternate

  • The exception is: you may skip it if the destination meets specific criteria

  • Think of the alternate as required unless you earn the exception


91.169(c) — what makes an airport legal as an alternate:

  • The alternate minimums (standard 600-2 / 800-2, or non-standard as published)

  • Governs which airports you may list

  • Separate from the question of whether you need one

  • Two questions: do I need one? and which ones qualify?


91.167 — the fuel consequence:

  • If an alternate is required, you must carry fuel to the destination, then to the alternate, then 45 minutes at normal cruise

  • The alternate decision drives the fuel calculation

  • Covered below


The Two Conditions for NOT Needing an Alternate

The 1-2-3 rule is famous, but it's only half of the exception. To legally skip the alternate, BOTH of these must be true at the destination:


Condition 1 — The destination has a published instrument approach

  • The destination must have a standard instrument approach procedure (a Part 97 approach — any published IAP)

  • If the destination has NO instrument approach, an alternate is ALWAYS required, regardless of how good the weather is forecast to be

  • Logic: without an approach, you have no way to get in if the weather is lower than forecast

  • The condition pilots forget


Condition 2 — The 1-2-3 rule is met

  • For the period from 1 hour before to 1 hour after your estimated time of arrival

  • The forecast ceiling is at least 2,000 feet above the airport elevation, AND

  • The forecast visibility is at least 3 statute miles

  • Throughout the entire two-hour window


If both are true: no alternate required (but you still carry destination fuel + 45 minutes)If either is false: an alternate is required


Why both matter:

  • A destination with a great forecast but no approach → alternate required

  • A destination with an ILS but a 1,500-foot forecast ceiling → alternate required

  • Only an approach AND 1-2-3 weather together let you skip it

  • Two gates


Applying the 1-2-3 Rule to the TAF

The rule is based on FORECAST weather, not current conditions. Here's how to actually apply it.


The window:

  • Compute your ETA at the destination

  • Look at the TAF for the period from 1 hour before to 1 hour after that ETA

  • Every forecast condition that applies during that window counts

  • Not just the exact ETA — the whole two hours


The simple question:

  • "From 1 hour before to 1 hour after my ETA, will the ceiling be at least 2,000 feet AND the visibility at least 3 miles — the entire time?"

  • Yes → no alternate required

  • No (at any point in the window) → alternate required


Handling TEMPO groups:

  • A TEMPO group (temporary fluctuations lasting less than an hour at a time) that overlaps your window and forecasts conditions below 2,000-3 COUNTS against you

  • FAA guidance treats TEMPO conditions as controlling for planning purposes

  • If the TEMPO says "TEMPO 1618 BKN015" and your window includes any of 16Z–18Z, the forecast ceiling is 1,500 — alternate required

  • Don't ignore TEMPO


Handling PROB groups:

  • A PROB30 (30% probability) group forecasting below-minimums weather in your window is treated conservatively — most instructors and examiners expect you to count it

  • The FAA's weather-briefing guidance is that PROB conditions should be considered in planning

  • If PROB30 shows 1,000 overcast in your window, file an alternate

  • When in doubt, the conservative reading wins


Handling BECMG and FM groups:

  • FM (from) is a hard change at the stated time — use the conditions in effect for each part of your window

  • BECMG (becoming) is a gradual change over the stated period — assume the worse of the two conditions during the transition period

  • Walk through the window hour by hour

  • Line up the TAF against the clock


What counts as "ceiling":

  • The lowest BKN (broken) or OVC (overcast) layer, or VV (vertical visibility)

  • FEW and SCT do not constitute a ceiling

  • A forecast of "SCT015 BKN025" has a 2,500-foot ceiling (the BKN layer)

  • Read the layers correctly


Weather sources for the rule:

  • The destination TAF (the primary source)

  • The Graphical Forecasts for Aviation (GFA — which replaced the old Area Forecasts) for airports without a TAF

  • A Flight Service briefing (which uses the same products)

  • Forecasts, not METARs


What if the destination has no TAF?

  • Many smaller airports have no TAF

  • Without a forecast, you cannot demonstrate that 1-2-3 is met for the window

  • The practical answer most examiners expect: file an alternate

  • Some pilots use a nearby TAF plus the GFA with judgment, but that doesn't satisfy the regulation's "appropriate weather forecasts" for that airport as cleanly — the conservative and defensible answer is to file one

  • No TAF = file an alternate


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Choosing a Legal Alternate: The Standard Alternate Minimums

Once you've determined an alternate is required, it must meet the alternate minimums in 91.169(c). These apply to the FORECAST at your ETA at the alternate (use the alternate's own TAF).


Standard alternate minimums (when no non-standard minimums are published):

Alternate with a precision approach (ILS, PAR, or GLS):

  • Forecast ceiling at least 600 feet

  • Forecast visibility at least 2 statute miles

  • "600-2"


Alternate with only non-precision approaches (VOR, LOC, NDB, LNAV, LP, and — for planning purposes — LPV and LNAV/VNAV without baro-VNAV):

  • Forecast ceiling at least 800 feet

  • Forecast visibility at least 2 statute miles

  • "800-2"


Alternate with no published instrument approach:

  • The forecast ceiling and visibility must allow a descent from the MEA, approach, and landing under BASIC VFR

  • You must be able to get down and land visually

  • Rare, but legal

  • The "VFR descent" alternate


The memory aid:

  • Precision: 600-2

  • Non-precision: 800-2

  • No approach: descend from the MEA under basic VFR

  • These are the standard values


The forecast-at-the-alternate point:

  • You check the ALTERNATE's forecast at your ETA at the ALTERNATE (not the destination's window)

  • Use the alternate's TAF

  • A different airport, a different forecast, a different time

  • Don't apply the destination's TAF to the alternate


The GPS and LPV Rules — Done Correctly

This is the most commonly misunderstood part of alternate planning, and it matters because getting it wrong produces an illegal alternate.


LPV is NOT a precision approach for alternate planning:

  • LPV (Localizer Performance with Vertical guidance) is an APV — an Approach with Vertical guidance — not a precision approach under the regulatory definition

  • When planning an RNAV (GPS) approach at an alternate, you may NOT plan on the LPV minimums

  • You must plan using the LNAV or circling MDA on that approach

  • Which puts you in the 800-2 (non-precision) category — never 600-2


Why the FAA does this:

  • Alternate planning builds in margin against GPS integrity issues (RAIM/WAAS availability) at the time you'd actually need the alternate

  • Planning on the higher LNAV minimums ensures the alternate is usable even if vertical guidance isn't available when you arrive

  • Conservative by design

  • The vertical guidance is a bonus you can use when you get there, not a planning credit


The one vertical-guidance exception:

  • You may plan on the LNAV/VNAV DA at the alternate ONLY if your aircraft has approved baro-VNAV (barometric vertical navigation) equipment and you're using it

  • Not WAAS vertical guidance — baro-VNAV specifically

  • Most light GA aircraft don't have approved baro-VNAV

  • For almost all GA pilots: plan on LNAV/circling MDA (800-2)


The equipment rule — non-WAAS GPS (TSO-C129 / TSO-C196):

  • Older, non-WAAS GPS receivers (with fault detection and exclusion and a RAIM prediction performed):

  • You may plan a GPS-based approach at the destination OR the alternate — but not both

  • One of the two airports must have an approach you can fly WITHOUT GPS (ILS, VOR, LOC, etc.) that your aircraft is equipped for

  • At the alternate, plan using the LNAV/circling MDA (800-2)

  • The "not at both" rule


The equipment rule — WAAS GPS (TSO-C145 / TSO-C146):

  • WAAS-equipped aircraft may plan RNAV (GPS) approaches at both the destination AND the alternate

  • No RAIM prediction required (WAAS provides integrity)

  • BUT — at the alternate, you still must plan using the LNAV or circling MDA, not LPV

  • WAAS removes the "not at both" restriction; it does NOT upgrade the alternate to 600-2


Putting the GPS rules together:

Equipment

GPS at destination AND alternate?

Minimums to plan at the alternate

Non-WAAS (TSO-C129/C196)

No — one or the other

LNAV or circling MDA (800-2)

WAAS (TSO-C145/C146)

Yes — both allowed

LNAV or circling MDA (800-2); LPV NOT allowed for planning

Baro-VNAV approved

Per the above

May use LNAV/VNAV DA


The practical takeaway:

  • Any RNAV (GPS) approach at your alternate = 800-2 for planning (unless baro-VNAV)

  • If you want a 600-2 alternate, it needs an ILS, PAR, or GLS

  • Once you actually divert and fly the approach, you may use whatever minimums (including LPV) the approach and your equipment support — the LNAV restriction is a PLANNING rule, not a flying rule

  • Plan on 800-2; fly to whatever you've got


Non-Standard Alternate Minimums and the Symbols

Not every airport uses the standard 600-2/800-2. Some publish non-standard minimums, and some can't be used as an alternate at all.


Where to look:

  • The approach chart's briefing strip/notes

  • The "IFR Alternate Airport Minimums" section at the front of the Terminal Procedures Publication (TPP)

  • Non-standard minimums are listed by airport and approach


The ⧊A symbol (triangle with an "A"):

  • On an approach chart, a black triangle with a white "A" means non-standard alternate minimums apply to that airport

  • Go to the TPP alternate minimums section to find them

  • They are always MORE restrictive than standard (higher ceiling, greater visibility, or both)

  • Often tied to the specific approach or to equipment (e.g., "ILS 600-2, LOC 800-2¼")


The "NA" designation:

  • Some airports (or specific approaches) are marked "Alternate Minimums NA" — not authorized as an alternate

  • Common reasons: no weather reporting at the airport, no approach-control monitoring, or the approach depends on a facility not available for alternate use

  • An "NA" airport CANNOT be filed as an alternate, regardless of the forecast

  • Check for it


The "A NA" on GPS approaches:

  • Some RNAV (GPS) approaches carry "A NA" because the airport lacks weather reporting, or the approach has specific restrictions

  • Can't be used as the alternate approach

  • Look for it on the chart

  • A frequent trap


Why non-standard minimums exist:

  • Terrain or obstacles making the approach less forgiving

  • Unmonitored navaids

  • Lack of local weather observation (you can't verify the forecast on arrival)

  • The airport is less reliable as a fallback than the standard assumes


The practical habit:

  • Every time you pick an alternate, check the chart for ⧊A and NA

  • Pull the TPP alternate minimums page if ⧊A is present

  • Don't assume 600-2/800-2 without looking

  • Two seconds of checking


Don't confuse ⧊A with the Trouble ⧊T:

  • ⧊A = non-standard ALTERNATE minimums

  • ⧊T = non-standard TAKEOFF minimums and/or an ODP

  • Both are "go look it up" flags, for different purposes

  • Know which is which



Alternate Minimums vs. Landing Minimums

A distinction that resolves a lot of confusion.


Alternate minimums (planning):

  • The forecast weather required at your ETA at the alternate to legally FILE it (600-2 / 800-2 / non-standard)

  • A planning threshold, applied before departure

  • Higher than the approach's landing minimums (built-in margin)

  • About filing, not flying


Landing minimums (flying):

  • The published DA or MDA and visibility on the approach you actually fly when you divert

  • Applied in the air, on the approach

  • Lower than the alternate minimums

  • About flying, not filing


Why they differ:

  • The alternate minimums add margin because you're planning against a forecast hours in advance

  • The landing minimums are what the approach actually supports when you're there

  • Once you divert, you fly the approach to its landing minimums — not to 600-2 or 800-2

  • Plan high, fly to the chart


The example:

  • You file an airport with an ILS as your alternate because its forecast is 700-3 (meets 600-2)

  • You divert there; the actual weather is 300-¾

  • You fly the ILS to its published DA (say 200 feet and ½ mile)

  • The 600-2 was for filing; the ILS minimums are for landing


The LPV connection:

  • You planned the alternate on LNAV minimums (800-2) because that's the rule

  • When you divert and fly the RNAV (GPS) approach, you may use LPV if it's available

  • The planning restriction doesn't limit the approach you fly

  • Plan conservatively, fly what you have


Fuel Requirements and Alternates (91.167)

Filing an alternate directly changes the fuel you must carry.


If an alternate is required, carry enough fuel to:

  1. Fly to the destination (including the approach)

  2. Fly from the destination to the alternate

  3. Fly 45 minutes at normal cruising speed after that


If no alternate is required:

  • Fuel to the destination plus 45 minutes

  • The 45-minute reserve applies either way

  • Skipping the alternate removes the alternate leg, not the reserve


The worked example:

  • Destination: 2:00 en route

  • Alternate: 0:30 from the destination

  • Reserve: 0:45

  • Required: 3:15 of fuel (minimum)

  • At 10 GPH: 32.5 gallons minimum aboard


The missed-approach reality:

  • The alternate leg realistically starts with a missed approach at the destination (climb, clean up, get a clearance)

  • Add fuel for the miss and the climb

  • The regulation's minimum assumes a clean diversion; real ones aren't

  • Plan above the minimum


Why the violation applies even if you never divert:

  • The fuel requirement is a PLANNING requirement

  • Departing without the required fuel aboard is a violation at the moment you depart

  • Whether you later need the alternate is irrelevant

  • Plan it, carry it


When an Alternate Isn't Required — But Is Still Wise

The regulation sets the floor. Judgment sets the standard.


Even with a 1-2-3 forecast, consider filing an alternate when:

  • The destination has a single runway (one closure or incident shuts the airport)

  • The destination has a single approach (one NOTAM takes it away)

  • NOTAMs affect approach lighting, navaids, or the runway

  • Terrain or obstacles make the approach demanding

  • The forecast is marginal or trending down

  • Thunderstorms, fog, or snow are in the picture

  • You're arriving at night


The cost of filing an alternate you don't need:

  • A few more gallons of fuel planning

  • Thirty seconds on the flight plan

  • That's it


The cost of not having one when you need it:

  • Improvising a diversion in IMC with declining fuel

  • The "where do I go?" problem at the worst moment

  • Pressure to continue a bad approach

  • Far higher


"An alternate may be legal to skip but still wise to file."

  • When in doubt, file one

  • It's free insurance

  • The professional habit


Takeoff Alternates vs. Destination Alternates

Two different concepts that share a word.


Destination alternate (this post):

  • Where you go if you can't land at the destination

  • Required under 91.169 when the two conditions aren't met

  • Applies to all IFR operations


Takeoff alternate:

  • Where you go if you have to return shortly after departure but the DEPARTURE airport is below LANDING minimums

  • Required for Part 121 (121.617) and Part 135 operators when departure weather is below landing minimums

  • Must be within 1 hour one-engine-inoperative for twins, 2 hours for 3+ engines

  • NOT required under Part 91 — but the logic ("can I get back in?") is the best personal-minimums tool for low-weather departures


Why the distinction matters:

  • Different triggers (departure weather vs. destination forecast)

  • Different regulations (121.617/135 vs. 91.169)

  • Different timing (immediate return vs. end of flight)

  • Don't conflate them


(For takeoff alternates in depth, see our takeoff minimums post.)

Part 121 and Part 135 Differences (Brief)


Commercial operators have parallel but stricter rules.

Part 121 (121.619):

  • The same 1-hour-before/after window and 2,000-3 concept for domestic operations

  • Alternate minimums come from the operator's OpSpecs (often derived from the published approach minimums with additives)

  • More conservative than Part 91 in practice

  • Flag operations have different rules


Part 135 (135.223 / 135.221):

  • Alternate required unless the destination forecast meets 1-2-3 for the 1-hour window

  • Alternate minimums per 135.221 and OpSpecs

  • Similar structure, tighter application


For the Part 91 pilot:

  • Know that the commercial rules exist and are stricter

  • The Part 91 rules (91.167/91.169) are what apply to you

  • The logic is the same; the margins differ

  • Borrow the conservatism


Checkride Questions — With Answers

"Explain the 1-2-3 rule."

  • An alternate is required unless, from 1 hour before to 1 hour after your ETA at the destination, the forecast ceiling is at least 2,000 feet AND visibility at least 3 SM — AND the destination has a published instrument approach. Both conditions are required to skip the alternate.


"What are the standard alternate minimums?"

  • Precision approach (ILS/PAR/GLS): 600-2. Non-precision approach: 800-2. No instrument approach: the forecast must allow a descent from the MEA and landing under basic VFR. Non-standard minimums (⧊A) override these.


"Can GPS be used at an alternate?"

  • Yes, with rules. Non-WAAS GPS: at the destination OR the alternate, not both. WAAS: at both. In either case, plan the alternate using the LNAV or circling MDA (800-2) — LPV cannot be used for alternate planning (it's an APV, not precision). LNAV/VNAV DA only with approved baro-VNAV.


"Does LPV make the alternate a 600-2 airport?"

  • No. LPV is not a precision approach for planning purposes. Any RNAV (GPS) approach at the alternate is planned at 800-2. You may fly the LPV when you get there.


"What if the destination has no TAF?"

  • You can't demonstrate 1-2-3 for the window without a forecast for that airport — file an alternate. (And if the destination has no instrument approach, an alternate is required regardless of forecast.)


"What if the TAF has a TEMPO below 2,000-3 in my window?"

  • It counts. TEMPO conditions are controlling for planning. File an alternate.


"Once you divert to the alternate, what minimums do you fly to?"

  • The approach's published landing minimums (DA/MDA), not the alternate minimums. The 600-2/800-2 were for filing. You may use LPV if available.


"What fuel is required with an alternate?"

  • Destination + alternate + 45 minutes at normal cruise (91.167). Without an alternate: destination + 45 minutes.


Common Pitfalls

  • Using current METARs instead of the TAF (the rule is forecast-based)

  • Checking only the exact ETA instead of the full 1-hour-before/after window

  • Ignoring TEMPO and PROB groups that dip below 2,000-3

  • Forgetting that a destination with no instrument approach always requires an alternate

  • Assuming "no TAF" means "no alternate needed" (it means the opposite)

  • Treating LPV as a precision approach for alternate planning (it's 800-2)

  • Planning GPS at both destination and alternate with a non-WAAS receiver

  • Not checking for ⧊A (non-standard) or NA (not authorized) at the alternate

  • Applying the destination's TAF to the alternate (use the alternate's own forecast at your ETA there)

  • Planning fuel only to the destination when an alternate is required

  • Confusing alternate minimums (filing) with landing minimums (flying)

  • Confusing a destination alternate with a takeoff alternate


Best Practices for Alternate Planning

  • File an alternate whenever the forecast is marginal, even if 1-2-3 is technically met

  • Choose alternates with multiple approaches and multiple runways

  • Prefer an alternate with an ILS if you want the 600-2 planning credit

  • Choose an alternate in a different weather regime from the destination (not 10 miles away under the same cloud deck)

  • Check ⧊A and NA every time

  • Use the alternate's own TAF at your ETA there

  • Plan fuel for a realistic missed approach plus the diversion, not just the regulatory minimum

  • Brief the alternate approach before departure as thoroughly as the destination approach

  • Re-evaluate in flight — the filed alternate is the floor, not a commitment


Conclusion

Alternate airport requirements are a cornerstone of IFR safety and risk management. The 1-2-3 rule is the trigger everyone remembers, but the full picture has more structure: the destination must have a published approach AND meet 1-2-3 across the entire two-hour window — read against the TAF including its TEMPO and PROB groups — or an alternate is required. The alternate itself must meet 600-2 (precision), 800-2 (non-precision), or its published non-standard minimums, and must not be marked NA. And for GPS: plan the alternate on LNAV or circling minimums at 800-2, because LPV is not precision for planning — non-WAAS users at one airport or the other, WAAS users at both.


Then carry fuel for the destination, the alternate, and 45 minutes — a requirement that binds the moment you depart. Smart pilots go further than the regulation: they file alternates in marginal weather even when legal to skip, they pick alternates with multiple approaches in a different weather regime, and they brief the alternate as carefully as the destination. Planning for the possibility of not landing where you intended is not pessimism — it's professionalism.


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On the Written Test and Checkride

Alternate requirements appear on every instrument written and oral. The most commonly tested topics:

  • The 1-2-3 rule and the two conditions for skipping an alternate (91.169)

  • Standard alternate minimums (600-2 precision, 800-2 non-precision)

  • The GPS rules (non-WAAS one-or-the-other; WAAS both; LNAV/circling minimums at the alternate; LPV not for planning)

  • Non-standard alternate minimums (⧊A) and NA

  • IFR fuel with an alternate (91.167)

  • Alternate minimums vs. landing minimums

  • Takeoff alternate vs. destination alternate


Quick Reference

The Regulation:

  • 91.169(b): when an alternate is required

  • 91.169(c): alternate minimums

  • 91.167: fuel


Two Conditions to SKIP an Alternate (both required):

  1. The destination has a published instrument approach (Part 97 IAP)

  2. The 1-2-3 rule: from 1 hr before to 1 hr after ETA, forecast ceiling ≥ 2,000 ft AND visibility ≥ 3 SM, throughout the window

  3. Either fails → alternate required

  4. No approach → alternate ALWAYS required

  5. No TAF → file an alternate


Reading the TAF for 1-2-3:

  • Use the FORECAST (TAF/GFA), not METARs

  • Check the whole 2-hour window

  • TEMPO below 2,000-3 in the window → counts (alternate required)

  • PROB30 below minimums in the window → treat conservatively (alternate required)

  • FM = hard change; BECMG = assume the worse condition during the transition

  • Ceiling = lowest BKN/OVC/VV (not FEW/SCT)


Standard Alternate Minimums (forecast at your ETA at the ALTERNATE):

Alternate has...

Required forecast

Precision approach (ILS, PAR, GLS)

600-2

Non-precision only (VOR, LOC, NDB, LNAV, LP — and GPS approaches for planning)

800-2

No instrument approach

Descend from MEA and land under basic VFR


GPS at the Alternate (the rules):

  • LPV is NOT precision for planning → plan on LNAV or circling MDA → 800-2

  • LNAV/VNAV DA only with approved baro-VNAV

  • Non-WAAS (TSO-C129/C196): GPS approach at destination OR alternate, not both; one airport needs a non-GPS approach

  • WAAS (TSO-C145/C146): GPS at both allowed; still plan the alternate on LNAV/circling (800-2)

  • Once you divert, FLY whatever minimums the approach supports (including LPV)


Non-Standard Minimums and Symbols:

  • ⧊A (triangle-A): non-standard ALTERNATE minimums — look them up in the TPP (always more restrictive)

  • NA: not authorized as an alternate (often no weather reporting) — cannot be filed

  • Don't confuse ⧊A with ⧊T (takeoff minimums/ODP)


Alternate vs. Landing Minimums:

  • Alternate minimums (600-2/800-2): for FILING (planning, before departure)

  • Landing minimums (DA/MDA): for FLYING the approach when you divert

  • Plan high, fly to the chart


Fuel (91.167):

  • With alternate: destination + alternate + 45 min at normal cruise

  • Without alternate: destination + 45 min

  • A planning violation at departure, whether or not you divert

  • Add fuel for a realistic missed approach


Takeoff Alternate (different thing):

  • For an immediate return when the DEPARTURE airport is below landing minimums

  • Part 121 (121.617) / 135: within 1 hr one-engine-out (twins), 2 hr (3+ engines)

  • Not required under Part 91 — but the logic is the best personal-minimums test


Legal to Skip but Wise to File:

  • Single runway or single approach at the destination

  • NOTAMs on approaches/lighting

  • Marginal or deteriorating forecast

  • Night, thunderstorms, fog, snow

  • Filing costs a few gallons; not having one can cost everything


Key Principle:

An alternate is required unless the destination has a published approach AND the forecast meets 1-2-3 (2,000 ft and 3 SM) for the full hour-before-to-hour-after window — read against the TAF including TEMPO and PROB. The alternate must meet 600-2 (precision), 800-2 (non-precision), or its published non-standard minimums, and not be NA. For GPS, plan the alternate on LNAV/circling at 800-2 — LPV never counts for planning — with non-WAAS at one airport or the other and WAAS at both. Carry destination + alternate + 45 minutes.



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Author: Nathan Hodell

CFI, CFII, MEI, ATP, Creator and CEO

Nathan is an aviation enthusiast with thousands of hours of flying and dual instruction over the past 15+ years. Through his aviation career he has been able to earn his ATP, fly as an airline pilot, own/operate flight schools, and create and host wifiCFI.



 
 
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