IFR Fuel Requirements (91.167): The Full Fuel Ledger, the 45-Minute Reserve, and What "Normal Cruise" Really Means
Updated: 6 days ago
Fuel planning under Instrument Flight Rules is more than a regulatory checkbox — it's a critical safety function that protects you from weather changes, approach delays, missed approaches, and diversions. IFR fuel requirements are built on an assumption VFR rules don't make: that things will go wrong. The destination approach might fail. ATC might hold you. The alternate might be farther than it looked. The regulation (14 CFR 91.167) sets a floor that accounts for a diversion and a 45-minute reserve, but the floor is just that — and the real skill is building a fuel plan that survives the realistic version of the flight, not the optimistic one.
This post covers IFR fuel requirements in practical depth: the purpose and the regulation, the three-part Part 91 rule, a complete worked fuel ledger in gallons, what "normal cruising speed" actually means, how the alternate decision changes the math, holding and delay buffers, the fuel-remaining entry on the flight plan, minimum fuel versus emergency fuel declarations, the Part 121/135 comparison, and the checkride questions with answers.
Study this full length lesson (video, podcast, flashcards, and quiz) here: Full Length Lesson >
The Purpose of IFR Fuel Requirements
IFR fuel rules exist to ensure that, when conditions don't go as planned, you still have options.
The rules ensure you can:
Complete the planned flight to the destination
Fly an approach — and a missed approach if it doesn't work
Divert to an alternate airport when one is required
Land with a meaningful fuel reserve still in the tanks
The assumption behind IFR fuel:
VFR fuel rules assume you'll see the airport and land
IFR fuel rules assume UNCERTAINTY: weather below forecast, holding, vectors, a missed approach, a diversion
The IFR planning model expects something to go wrong
The reserve and the alternate leg are the margin for that
Why fuel is different from other IFR planning:
Most IFR decisions can be revisited in flight (a different approach, a different altitude, a different airport)
Fuel can't be added in flight
Every option you'll have later depends on fuel you loaded before departure
The one decision that's truly locked at takeoff
Regulatory Basis (United States)
Part 91:
14 CFR 91.167 — Fuel requirements for flight in IFR conditions
The general aviation rule
The subject of this post
Commercial operators:
Part 121 (121.639 domestic, 121.645 flag/supplemental) — air carriers
Part 135 (135.223) — commuter and on-demand
Separate, often more restrictive, built on the same concepts
Compared below
The related regulations:
91.169 — when an alternate is required (the 1-2-3 rule) and alternate minimums — this drives the fuel calculation
91.151 — VFR fuel (30 minutes day, 45 minutes night) for contrast
91.103 — preflight action (fuel requirements are an explicit item — the "F" in WKFARTN)
The fuel rule doesn't stand alone
The Part 91 IFR Fuel Rule (91.167)
Under Part 91, no person may operate under IFR unless the aircraft carries enough fuel (considering weather reports, forecasts, and conditions) to:
Fly to the first airport of intended landing (the destination)
Fly from that airport to the alternate airport (if an alternate is required)
Fly after that for 45 minutes at normal cruising speed
The three legs:
Destination leg
Alternate leg (conditional on whether an alternate is required)
45-minute reserve (always)
The reserve is mandatory regardless of weather:
Whether or not an alternate is required, the 45 minutes applies
Good weather removes the alternate leg, not the reserve
The reserve is the constant
45 minutes, always
The helicopter difference:
For helicopters under IFR, the reserve is 30 minutes (not 45)
Same structure (destination, alternate, reserve), shorter reserve
Reflects the helicopter's landing-site flexibility
Airplanes: 45; helicopters: 30
The "considering weather reports and forecasts" clause:
The regulation requires you to account for the weather and conditions known at planning
Forecast headwinds, forecast delays, known routing — all part of the "enough fuel" determination
Not just distance ÷ speed × burn
A judgment-informed requirement
When an Alternate Is Required (Quick Review)
Fuel planning is inseparable from the alternate decision, because the alternate adds a leg.
The two conditions to skip an alternate (91.169):
The destination has a published instrument approach, AND
The 1-2-3 rule is met: from 1 hour before to 1 hour after your ETA, the forecast ceiling is at least 2,000 feet and visibility at least 3 SM
If either fails → alternate required → add the alternate leg to the fuel plan.
The fuel consequence:
Alternate required: destination + alternate + 45 min
No alternate required: destination + 45 min
The alternate decision can add 30–60 minutes of fuel to the requirement
Decide the alternate first, then compute fuel
(For the full alternate rules — minimums, the GPS/LPV planning rule, TAF reading — see our alternate airport post.)
The Complete IFR Fuel Ledger: A Worked Example
Here's what the original describes but doesn't show — the actual arithmetic, segment by segment, in gallons. Build this once and the regulation makes sense forever.
The aircraft and conditions:
Normally aspirated single, cruise burn 10 GPH at normal cruise power
Climb burn 14 GPH; taxi/run-up about 1.5 gallons
Usable fuel aboard: 50 gallons (300 lb)
The flight:
Destination: 180 NM, planned 1:45 en route at 105 kt groundspeed (headwind)
Destination forecast at ETA: 1,200 broken, 3 SM → alternate required (ceiling below 2,000)
Alternate: 40 NM from the destination, about 0:25 at cruise
Alternate forecast: 1,500 overcast, 4 SM, ILS available → meets 600-2
The ledger:
Segment | Time | Burn | Gallons |
Taxi, run-up, takeoff | — | — | 1.5 |
Climb to cruise (to 8,000) | 0:12 | 14 GPH | 2.8 |
Cruise to destination | 1:33 | 10 GPH | 15.5 |
Approach at destination (vectors, descent, approach) | 0:15 | 10 GPH | 2.5 |
Missed approach and climb-out | 0:05 | 14 GPH | 1.2 |
Cruise to alternate | 0:25 | 10 GPH | 4.2 |
Approach at alternate | 0:12 | 10 GPH | 2.0 |
Subtotal — fuel to use | 2:42 | 29.7 | |
45-minute reserve at normal cruise | 0:45 | 10 GPH | 7.5 |
Regulatory minimum aboard at departure | 37.2 | ||
Holding/delay buffer (personal) | 0:20 | 10 GPH | 3.3 |
Headwind-worse-than-forecast buffer (personal) | — | — | 2.0 |
Planned fuel aboard | 42.5 |
Reading the ledger:
The regulation requires 37.2 gallons aboard (the subtotal plus the reserve)
With 50 usable, you're legal with about 13 gallons of margin
The personal buffers (holding, winds) bring the plan to 42.5 — you'd land at the alternate with about 15 gallons (1.5 hours), or at the destination with about 22
Legal and comfortable
What the ledger teaches:
The approach and missed approach at the destination are real fuel (about 4 gallons here) that a "distance ÷ speed" plan misses
The alternate leg includes its own approach — not just the cruise distance
Climb fuel is higher than cruise fuel; don't average it away
The reserve is computed at CRUISE burn (10 GPH), not an economy setting
Buffers go on top of the legal minimum, not inside it
The "assume the destination landing fails" principle:
Plan the fuel as if you WILL miss at the destination and WILL go to the alternate
If you land at the destination, you simply have more fuel than planned
Never plan on the optimistic outcome
The pessimistic plan is the safe one
What "Normal Cruising Speed" Actually Means
The 45-minute reserve is defined at "normal cruising speed," and the wording matters.
What it is:
The reserve is 45 minutes of fuel at your NORMAL cruise power setting and the fuel flow that goes with it
The fuel you'd burn flying 45 minutes the way you actually cruise
Realistic cruise consumption
In the ledger above: 45 minutes × 10 GPH = 7.5 gallons
What it is NOT:
NOT 45 minutes at holding speed (lower power, lower burn)
NOT 45 minutes at best-economy or maximum-endurance power
NOT 45 minutes at a reduced "I'll lean it way back" setting
Not the minimum you could stretch 45 minutes to
Why the distinction matters:
Computing the reserve at a low-power setting SHRINKS the gallons required (45 minutes at 6 GPH is 4.5 gallons instead of 7.5)
That makes you "legal" with less fuel — and leaves you with a smaller real margin
The FAA's reading is that "normal cruising speed" means your realistic cruise, which prevents this
The rule is written to produce a meaningful quantity of fuel, not a minimum one
The practical standard:
Use the POH cruise performance data at your planned cruise power
Use the fuel flow you actually see in cruise (if it's higher than the book, use the higher number)
Be conservative with the number
A reserve computed honestly is a reserve that's actually there
Fuel Planning Without an Alternate
When the destination meets 1-2-3 and has an approach, the alternate leg drops out — but careful planning doesn't.
The requirement:
Destination leg (including the approach) + 45 minutes
No alternate leg
Still the full reserve
What to still include:
The approach at the destination (vectors, descent, the procedure)
A missed approach — because "no alternate required" means the forecast was good, not that the approach is guaranteed
Realistic holding or delay buffers (a 2,000-3 forecast doesn't prevent ATC delays)
The reserve at normal cruise
The "no alternate" trap:
Pilots sometimes read "no alternate required" as "plan fuel to the destination and the reserve, done"
But the destination can still go bad (forecast busts, a runway closure, an approach NOTAM)
Without a filed alternate, your diversion is improvised — make sure you have fuel to improvise with
"Not required" doesn't mean "not needed"
The best practice:
Even without a required alternate, know where you'd go and whether you have fuel to get there
Many pilots plan fuel to a "mental alternate" regardless
The regulation sets the minimum; the realistic plan sets the fuel
Plan for the diversion you hope not to make
Holding, Delays, and the Buffers the Regulation Doesn't Mention
The regulation requires fuel for the legs and the reserve — not for holding, vectors, or reroutes. Those are on you.
What IFR operations routinely add:
Holding (weather, traffic, a runway change) — 10 to 30 minutes is common at busy airports
Vectors for sequencing (an extended downwind can add 10 NM)
Approach delays (waiting for a slot)
Weather reroutes (around convective activity)
A second approach attempt
None of these are in the regulatory minimum:
91.167 doesn't require holding fuel
A pilot carrying exactly the legal minimum has NO fuel for any delay without eating into the reserve
The regulation assumes a clean flight; real flights aren't
The buffer is your responsibility
The planning approach:
Add a holding buffer (15–30 minutes at busy destinations, more if ATC delays are forecast — the "K" in WKFARTN)
Add a wind buffer (forecast winds are often wrong by 10–20 knots)
Add a reroute buffer when weather is convective or the route is likely to be amended
Stack the buffers on top of the legal minimum
The ATC-delay information:
Known ATC delays (ground delay programs, flow restrictions) are part of required preflight (91.103)
If delays are forecast, the regulation's "considering conditions" clause arguably requires you to fuel for them
At minimum, they're a planning input
Check them
Forecast winds:
A headwind 20 knots stronger than forecast on a 2-hour leg adds 15–20 minutes of flight time
That's 2.5–3.5 gallons in the example aircraft — a third of the reserve
Use the forecast winds, then add margin for them being wrong
Winds are the most common reason real burn exceeds planned burn
Fuel Planning at the Alternate
The alternate leg has its own requirements beyond "can I reach it?"
The alternate must:
Be reachable with the fuel aboard after a missed approach at the destination
Have forecast weather meeting its alternate minimums at your ETA there (600-2 / 800-2 / non-standard)
Have an approach you can fly (and for GPS, planned at LNAV/circling minimums)
Leave the 45-minute reserve intact after landing there
Choosing the alternate with fuel in mind:
A CLOSE alternate (20–40 NM) costs little fuel and leaves a large margin
A DISTANT alternate (100+ NM) can consume most of your margin — and if it's also marginal weather, you've traded one problem for another
Prefer close, reliable alternates in a different weather regime
Distance is fuel
The alternate's approach fuel:
Include the approach at the alternate in the plan (vectors, descent, the procedure)
A 10–15 minute allowance is realistic
Not just the cruise distance between airports
The alternate leg ends on the runway, not over the airport
The "alternate too far" mistake:
Pilots sometimes pick an alternate for its weather alone, ignoring that it's 90 minutes away
The fuel math makes it marginal or impossible
Weather AND distance both matter
Run the ledger for each candidate
RNAV Procedures and Fuel
Modern approaches add flexibility — and sometimes distance.
Where RNAV procedures add fuel:
Missed approaches that route to a distant holding fix (some RNAV misses are 10+ NM)
"T" or "TAA" approaches with long initial segments from the IAF
Step-down fixes that extend the descent profile
Holding fixes built into the procedure (hold-in-lieu)
The planning adjustment:
Look at the actual approach plate for the destination and alternate
Measure the missed approach routing (where does it take you, and how far?)
Allow for the full procedure, not an idealized straight-in
The plate tells you the fuel
Why it matters:
A missed approach to a hold 12 NM away, plus the hold, plus the return for a second attempt or the diversion, can easily be 15 minutes
That's 2.5 gallons in the example — real fuel
Plan it
The procedure is the fuel
The Fuel-Remaining Entry on the Flight Plan
The ICAO flight plan asks for fuel endurance — and it's in TIME, for a reason.
Item 19 — Endurance:
Total usable fuel aboard, expressed in HOURS AND MINUTES (not gallons)
Example: 4 hours 15 minutes
Computed as usable fuel ÷ cruise burn rate (50 gal ÷ 10 GPH = 5:00)
The endurance you have at departure
Why time, not gallons:
Search and rescue uses it to know how long you could have flown — when to start looking, how far you could have gone
Gallons mean nothing to a rescue coordinator who doesn't know your aircraft
Time is universal
It's for SAR, not ATC
The accuracy point:
Enter the actual endurance at your planned cruise burn
Don't pad it — SAR plans around it
Be honest
It's a safety number
The in-flight habit:
Know your fuel remaining in TIME at all times
"I have 2 hours of fuel" is more useful than "I have 20 gallons" when ATC asks or when you're deciding to divert
Convert gallons to time continuously
Think in minutes
Monitoring Fuel in Flight
The plan is only as good as the monitoring.
The in-flight discipline:
Note the fuel at takeoff (gallons and time)
Track burn against the plan at each checkpoint (are you ahead or behind?)
Compare the fuel gauges to the calculation (the calculation is primary; the gauges are the cross-check)
Recompute the fuel remaining in time regularly
The decision points:
Set a "bingo" — the fuel quantity (or time) at which you WILL divert — before departure, and honor it
Brief fuel status before starting the approach ("I have 1:20 remaining, enough for the approach, a miss, and the alternate with reserve")
If a hold is assigned, compute how long you can hold before the alternate becomes marginal, and tell ATC
Decide early, not late
The "brief fuel before the approach" habit:
Before beginning an approach, state your fuel in time and confirm it covers: the approach, a missed approach, the alternate, and the reserve
If it doesn't, you're already in a minimum-fuel situation — act now
The approach briefing should include fuel
A professional habit
The reserve is not usable fuel:
The 45-minute reserve is the fuel you land WITH, not fuel you plan to USE
If you're planning to burn into the reserve, you've already failed the plan
Treat the reserve as the bottom of the tank
Land before you touch it
Minimum Fuel vs. Emergency Fuel
Two declarations with different meanings and different results.
"Minimum fuel" (an advisory):
Tells ATC you can accept NO UNDUE DELAY — any further delay (holding, extended vectors) will put you in a fuel emergency
It is NOT an emergency declaration and does NOT get you priority handling
It's a heads-up that you're down to your reserve plus a little
Phraseology: "[Call sign], minimum fuel"
What minimum fuel gets you:
ATC awareness — they'll try to avoid delaying you
No priority (other aircraft aren't moved for you)
A documented warning that you're tight
Not much, honestly — which is why you don't want to wait until you need it
"Emergency fuel" (a declaration):
You need PRIORITY handling to land with your reserve intact (or you're going to land below it)
A genuine emergency declaration
Gets you priority: direct routing, the approach you need, traffic moved
Phraseology: "[Call sign], declaring an emergency, low fuel" (or "Mayday" if the situation is grave)
What a fuel emergency gets you:
Priority handling and ATC's full assistance
A possible report afterward (not a punishment — a report)
The runway, now
Use it when you need it
The decision logic:
You're approaching your reserve and ATC assigns a hold → "minimum fuel" (and ask how long)
You're going to land below the reserve, or you're down to it with the destination still uncertain → declare the emergency
Declare EARLY — ATC can help a lot with 30 minutes of warning and very little with 5
Early is good decision-making, not failure
The paperwork myth:
Pilots sometimes delay declaring to avoid "paperwork"
A fuel emergency rarely results in enforcement when the pilot acted prudently and reported honestly
Fuel exhaustion ALWAYS results in an accident report
The paperwork is not the risk; the fuel is
Part 121 and Part 135: The Comparison
Commercial operators have parallel rules with more structure.
Part 121 domestic (121.639):
Fuel to the destination
Fuel to the most distant alternate (if required)
45 minutes at normal cruise after that
Plus the operator's own holding/contingency policies via OpSpecs and dispatch
Dispatch shares the fuel decision with the captain
Part 121 flag/supplemental (121.645):
For flag operations: destination, then an additional 10% of the total time to destination, then the alternate, then 30 minutes of holding at 1,500 feet above the alternate
A different structure for long international flights
More complex
Part 135 (135.223):
Destination, alternate (if required), then 45 minutes at normal cruise
Essentially the Part 91 structure
With OpSpecs refinements
The lesson for Part 91 pilots:
The commercial world adds dispatch oversight, contingency fuel, and defined holding fuel on top of the regulatory legs
Part 91 leaves all of that to you
Borrow the structure: contingency buffer, holding fuel, a defined reserve you don't touch
Fly like there's a dispatcher checking your math
What If the Weather Improves En Route?
The question the original poses but doesn't answer.
The regulatory timing:
91.167's fuel requirement is evaluated at the planning/departure point, based on the weather reports and forecasts available then
You must DEPART with the required fuel (destination + alternate + reserve, if an alternate was required at planning)
Weather improving en route doesn't retroactively change what you were required to carry — you carried it, you're compliant
The decision point was takeoff
What improving weather changes:
You may no longer NEED the alternate — the fuel you carried for it becomes additional margin
You may amend your flight plan (drop the alternate) if the destination now meets 1-2-3 — ATC doesn't care about your alternate, but your own plan can update
You can't "un-carry" the fuel, and you wouldn't want to
More fuel is never a problem
What deteriorating weather changes:
If the destination forecast WORSENS en route, you're now flying toward a destination that may need an alternate you didn't fuel for
Reassess: do you have fuel for an approach, a miss, a diversion, and the reserve?
If not, you're in a developing minimum-fuel situation — act early (divert while you still have options)
Deteriorating weather is the dangerous case
The answer for the checkride:
The fuel requirement is met or not met at departure, based on the planning forecast
Improving weather makes the carried alternate fuel extra margin
Deteriorating weather requires in-flight reassessment and possibly an early diversion
Fuel is planned at takeoff; judgment continues all the way to landing
Common IFR Fuel Planning Mistakes
Planning fuel only to the destination (forgetting the alternate leg when one is required)
Forgetting the approach and missed approach at the destination (3–5 gallons in a typical single)
Forgetting the approach at the alternate (the leg ends on the runway, not over the airport)
Computing the reserve at a low-power/economy setting instead of normal cruise
Using optimistic (book-minimum) fuel burn numbers instead of what the airplane actually burns
Ignoring forecast winds aloft (and not buffering for them being wrong)
Choosing an alternate too far away for the fuel aboard
Carrying exactly the legal minimum with no buffer for holding or vectors
Treating the 45-minute reserve as usable fuel to be planned into
Entering an inflated endurance on the flight plan
Waiting too long to declare minimum fuel or an emergency
Not briefing fuel before the approach
Best Practices for IFR Fuel Planning
Build the full ledger (taxi, climb, cruise, approach, missed, alternate, alternate approach, reserve) — don't shortcut it
Compute the reserve at your real cruise burn
Add buffers for holding (15–30 min), winds, and reroutes on top of the legal minimum
Plan to land with at least 1 hour of fuel, not 45 minutes
Choose close, reliable alternates in a different weather regime
Plan as if you WILL miss at the destination
Set a bingo fuel before departure and honor it
Brief fuel in time before every approach
Monitor burn against plan at every checkpoint; the calculation is primary, gauges are the cross-check
Declare minimum fuel or an emergency early
Reassess fuel whenever the destination weather changes en route
Checkride Questions — With Answers
"What are the IFR fuel requirements?"
Under 91.167, enough fuel to fly to the destination, then to the alternate (if one is required), then 45 minutes at normal cruising speed. Helicopters: 30 minutes.
"How does an alternate affect fuel planning?"
If an alternate is required (destination lacks an approach or the 1-2-3 forecast isn't met), you must add the fuel to fly from the destination to the alternate — realistically including a missed approach at the destination and an approach at the alternate — before the 45-minute reserve.
"What does the 45-minute reserve represent?"
The fuel you must still have aboard after reaching the destination (or alternate) — computed at your normal cruise fuel flow, not a reduced power setting. It's the margin for the unexpected, not fuel you plan to use.
"What does 'normal cruising speed' mean?"
Your realistic cruise power setting and its fuel flow — not holding, economy, or reduced-power consumption. It prevents shrinking the reserve by computing it at a low burn rate.
"What if the weather improves en route?"
The fuel requirement was evaluated at departure based on the planning forecast; you're compliant because you carried it. The alternate fuel becomes extra margin, and you may amend your plan. If weather deteriorates instead, reassess and divert early if needed.
"What's the difference between minimum fuel and emergency fuel?"
Minimum fuel is an advisory that you can accept no undue delay — it gets ATC awareness but no priority. Emergency fuel is a declaration that you need priority to land with your reserve — it gets priority handling. Declare early either way.
"How is fuel entered on the flight plan?"
As endurance in hours and minutes (Item 19), computed as usable fuel ÷ cruise burn. It's for search and rescue, so enter it honestly.
Conclusion
IFR fuel requirements are designed to protect you from the unpredictable nature of instrument flight. The regulation is simple — destination, alternate if required, 45 minutes at normal cruise — but the honest version of that plan has more line items than most pilots write down: the climb, the approach at the destination, the missed approach, the leg to the alternate, the approach at the alternate, and a reserve computed at real cruise burn rather than a flattering economy setting. Build the ledger once in gallons and the structure becomes permanent.
Then go beyond the minimum: buffer for holding and winds, plan to land with an hour rather than 45 minutes, pick a close and reliable alternate, brief your fuel in time before every approach, set a bingo and honor it, and declare early when the margin thins. Fuel should never be the limiting factor in a decision — because once it is, your options disappear faster than any other problem in the airplane can take them away.
On the Written Test and Checkride
IFR fuel requirements appear on every instrument written and oral. The most commonly tested topics:
The 91.167 three-part rule (destination, alternate if required, 45 minutes)
The helicopter difference (30 minutes)
The link to the alternate requirement (91.169 / 1-2-3)
"Normal cruising speed" (not a reduced setting)
The reserve is not usable fuel
Minimum fuel vs. emergency fuel
Fuel endurance on the flight plan (in time)
Quick Reference
91.167 — IFR Fuel (Part 91):
Fuel to the destination
Fuel to the alternate (if required by 91.169)
45 minutes at normal cruising speed
Airplanes: 45 min; helicopters: 30 min
Evaluated at departure, considering weather reports/forecasts
The Alternate Link (91.169):
Alternate required unless the destination has an approach AND the 1-2-3 forecast is met
Alternate required → add the alternate leg
No alternate → destination + 45 min (reserve always applies)
The Full Fuel Ledger (what to include):
Taxi/run-up/takeoff
Climb (at climb burn, not cruise)
Cruise to destination (at forecast groundspeed)
Approach at destination
Missed approach and climb-out
Cruise to alternate
Approach at alternate
= Fuel to use
45-min reserve at normal cruise burn
= Regulatory minimum aboard
holding buffer (15–30 min), wind buffer, reroute buffer
= Planned fuel aboard
Worked Example (10 GPH single, alternate required):
Fuel to use: ~29.7 gal (2:42)
Reserve: 7.5 gal (0:45)
Regulatory minimum: ~37.2 gal
With buffers: ~42.5 gal planned
"Normal Cruising Speed":
Your realistic cruise power and fuel flow
NOT holding, economy, or reduced power
Prevents shrinking the reserve with a low burn rate
Use the POH cruise data (or your actual observed burn if higher)
The Reserve:
The fuel you land WITH, not fuel you plan to USE
45 minutes at normal cruise
Treat it as the bottom of the tank
Plan to land with 1 hour (personal standard)
Buffers the Regulation Doesn't Require (but you need):
Holding: 15–30 min at busy destinations
Winds: forecast is often 10–20 kt off
Reroutes: convective weather
Stack them on top of the legal minimum
Flight Plan Endurance (Item 19):
Usable fuel ÷ cruise burn = hours and minutes
For search and rescue — enter honestly
Think in TIME in flight
Minimum Fuel vs. Emergency Fuel:
Declaration | Meaning | What it gets you |
"Minimum fuel" | Can accept no undue delay | ATC awareness, no priority |
"Declaring an emergency, low fuel" | Need priority to land with reserve | Priority handling |
Declare EARLY — 30 minutes of warning helps; 5 doesn't
Weather Changes En Route:
Improves: carried alternate fuel becomes margin; may amend the plan
Deteriorates: reassess fuel for approach + miss + divert + reserve; divert early if short
The requirement was met at departure; judgment continues to landing
Part 121/135 (comparison):
121 domestic: destination + most distant alternate + 45 min (+ dispatch contingency)
121 flag: destination + 10% of time + alternate + 30 min hold at 1,500 ft
135: destination + alternate + 45 min (Part 91 structure)
Lesson: add contingency and holding fuel like the airlines do
Key Principle:
IFR fuel (91.167) = destination + alternate (if required) + 45 minutes at normal cruising speed — with the reserve computed at your real cruise burn, never a reduced setting. Build the full ledger: climb, approach, missed approach, alternate leg, alternate approach, then the reserve, then buffers for holding and winds. Plan as if you'll miss at the destination, land with an hour, brief fuel before every approach, and declare early. Fuel is the one decision locked at takeoff.
Study Full Aviation Courses:
wifiCFI's full suite of aviation courses has everything you need to go from brand new to flight instructor and airline pilot! Check out any of the courses below for free:
Study Courses:
Checkride Lesson Plans:
Teaching Courses:
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.