FAR Explainer · 91.167
14 CFR 91.167 — IFR Fuel Requirements (Explained)
How much fuel you must carry for an IFR flight under 14 CFR 91.167 — destination + alternate + 45 minutes — and when the alternate fuel is not required.
Practice questions on this regulation
Get DPE-style scenario questions that exercise this rule in context.
14 CFR 91.167 — IFR Fuel Requirements (Explained)
What does 14 CFR 91.167 require for IFR fuel?
14 CFR 91.167(a) requires every aircraft operated under IFR to carry enough fuel to complete three sequential legs before departure. The rule is additive — you stack each requirement on top of the last, not choose between them.
The three requirements are:
- 1Reach the first airport of intended landing (destination fuel).
- 2Fly from the destination to the alternate airport, if an alternate is required under 14 CFR 91.169 (alternate fuel).
- 3Fly for 45 minutes at normal cruising speed after reaching the alternate — or 30 minutes for helicopters (final reserve).
The regulation uses the phrase "normal cruising speed," which means the cruise power setting entered on your flight plan — not maximum speed or published book values. A DPE will often ask you to walk through this calculation for your planned route.
When is the alternate fuel leg not required under 91.167(b)?
The alternate fuel requirement is waived by 14 CFR 91.167(b) when two conditions are met simultaneously at the destination airport.
Condition 1: A standard or special instrument approach procedure must be published for the destination airport.
Condition 2: Weather forecasts must indicate that from 1 hour before to 1 hour after the estimated time of arrival (ETA), the ceiling will be at least 2,000 feet above the airport elevation and the visibility will be at least 3 statute miles.
| Aircraft Type | Ceiling Requirement | Visibility Requirement | Time Window |
|---|---|---|---|
| Fixed-wing | 2,000 ft above airport elevation | 3 statute miles | 1 hr before to 1 hr after ETA |
| Helicopter | 1,000 ft above airport elevation (or 400 ft above lowest approach minimum, whichever is higher) | 2 statute miles | At ETA and 1 hr after ETA |
If both conditions are met, you do not carry alternate fuel and you do not list an alternate on the IFR flight plan. If either condition fails — no published approach, or forecast weather below those thresholds — you must carry alternate fuel and file an alternate per 14 CFR 91.169.
How does 91.167 connect to the alternate airport requirements in 91.169?
14 CFR 91.167 governs fuel quantity. 14 CFR 91.169 governs the IFR flight plan and when an alternate airport must be listed. The two rules use nearly identical exception language, which is why they are always discussed together.
The practical effect: if you satisfy the (b) exception in 91.167, you will also satisfy the equivalent exception in 91.169, and vice versa. When the exception does not apply, 91.169(c) sets the weather minimums the alternate airport itself must be forecast to meet for planning purposes — 600-foot ceiling and 2 sm visibility for precision approach alternates, 800-foot ceiling and 2 sm visibility for nonprecision approach alternates.
Knowing where 91.167 ends and 91.169 begins is a common oral exam distinction. 91.167 asks: "How much fuel?" 91.169 asks: "Does the flight plan need an alternate, and does that airport qualify?"
Worked example: calculating 14 CFR 91.167 fuel for a typical IFR flight
Consider a flight from KCVG to KLEX in a Cessna 172 burning 8.5 gallons per hour at normal cruise.
- Leg 1 — Destination: KCVG to KLEX is approximately 80 nm. At 110 kt cruise, flight time is roughly 44 minutes. Fuel required: 8.5 gph × 0.73 hr ≈ 6.2 gallons.
- Leg 2 — Alternate: KLEX TAF forecasts 900-foot overcast and 1.5 sm at ETA +1 hr, so the (b) exception does not apply. The filed alternate is KSDF (Louisville). KLEX to KSDF is approximately 75 nm, about 41 minutes. Fuel required: 8.5 × 0.68 ≈ 5.8 gallons.
- Leg 3 — 45-minute reserve: 8.5 gph × 0.75 hr = 6.4 gallons.
- Total minimum fuel required: 6.2 + 5.8 + 6.4 = 18.4 gallons.
The Cessna 172 holds 53 usable gallons in the standard configuration, so 18.4 gallons is well within capacity — but the regulation sets the floor, not the ceiling. Most pilots carry significantly more to account for holds, re-routes, and personal minimums.
What does a DPE ask about 14 CFR 91.167 on the oral exam?
DPEs approach 91.167 from two directions: regulatory knowledge and scenario application. Expect the examiner to give you a destination, a TAF, and ask whether you need an alternate — then follow up with the fuel calculation.
Common examiner questions include:
- Cite the regulation — 'What FAR governs IFR fuel requirements?' The answer is 14 CFR 91.167.
- Exception test — 'Your destination TAF shows 1,500 overcast and 4 sm at ETA. Do you need an alternate?' (Answer: yes — ceiling is below 2,000 feet, so the exception does not apply.)
- Exception test — 'TAF shows ceiling 3,000, visibility 5 sm throughout your window. Do you need alternate fuel?' (Answer: no — both thresholds exceeded, exception applies.)
- Calculation — 'Walk me through how you determined the fuel required for this flight.'
- Distinction — 'What is the difference between 91.167 and 91.169?' (Fuel quantity vs. flight plan requirements.)
- Definition — 'What speed do you use for the 45-minute reserve?' (Normal cruising speed.)
Practice Questions
- 1
Under 14 CFR 91.167(a), what three fuel legs must a fixed-wing aircraft carry for an IFR flight that requires an alternate airport?
Examiner GuidanceFuel to reach the destination, fuel to fly from the destination to the alternate airport, and fuel to cruise for 45 minutes at normal cruising speed after reaching the alternate. - 2
The TAF for your destination shows ceiling 1,800 feet and visibility 4 statute miles at your ETA. Under 91.167(b), must you carry alternate fuel?
Examiner GuidanceYes. The ceiling of 1,800 feet is below the 2,000-foot threshold required by 91.167(b). Because that condition is not met, the exception does not apply and you must carry fuel to reach an alternate. - 3
Your destination has no published instrument approach procedure. What does 91.167(b) require?
Examiner GuidanceBecause no standard or special instrument approach procedure is published for the destination, the (b) exception cannot apply regardless of the forecast weather. You must carry alternate fuel. - 4
You are flying a piston helicopter IFR. What is the final fuel reserve required by 91.167(a)(3)?
Examiner Guidance30 minutes at normal cruising speed. The regulation specifies 45 minutes for fixed-wing aircraft and 30 minutes for helicopters. - 5
Your destination TAF shows ceiling 2,500 feet and visibility 5 statute miles for the window from 1 hour before to 1 hour after your ETA. A standard ILS approach is published. Under 91.167(b), must you carry alternate fuel?
Examiner GuidanceNo. Both conditions of the (b) exception are met: a standard approach procedure exists and the forecast exceeds 2,000 feet ceiling and 3 statute miles for the required window. No alternate fuel is required.
Frequently Asked Questions
Q: What are the three fuel requirements under 14 CFR 91.167?
Under 14 CFR 91.167(a), you must carry enough fuel to: (1) reach the destination airport, (2) fly from the destination to the alternate airport if one is required, and (3) fly for 45 additional minutes at normal cruising speed. Helicopters substitute 30 minutes for the final reserve.
Q: When is the alternate airport fuel not required under 91.167?
The alternate fuel leg is not required if the destination has a published instrument approach procedure and weather forecasts show a ceiling of at least 2,000 feet AGL and visibility of at least 3 statute miles from 1 hour before to 1 hour after your ETA per 14 CFR 91.167(b).
Q: Does 14 CFR 91.167 apply to VFR flights?
No. Section 91.167 applies only to aircraft operated under IFR. VFR fuel requirements are governed by 14 CFR 91.151, which uses different daytime and nighttime reserves.
Q: What speed is used to calculate the 45-minute fuel reserve?
14 CFR 91.167(a)(3) specifies "normal cruising speed" — the cruise power setting you plan to use for the flight, not maximum speed or a published performance table value. Use the speed you enter on your flight plan.
Q: Do you have to file an alternate to satisfy 91.167?
Filing an alternate on the IFR flight plan (governed by 14 CFR 91.169) and carrying alternate fuel under 91.167 are related but separate requirements. If the (b) exception applies, you do not file an alternate and you do not carry fuel to reach one.
Q: What ceiling and visibility numbers trigger the 91.167(b) exception?
For fixed-wing aircraft, the forecast must show a ceiling at least 2,000 feet above the airport elevation and visibility at least 3 statute miles for the period from 1 hour before to 1 hour after the ETA per 14 CFR 91.167(b).
Q: What is the difference between 91.167 and 91.169?
14 CFR 91.167 defines how much fuel to carry for an IFR flight. 14 CFR 91.169 defines when an alternate airport must be listed on the IFR flight plan and what weather minimums that alternate must meet for planning purposes.
Q: Can I use fuel onboard before departure to meet 91.167?
No. The fuel must be on board at the point of departure. The regulation requires the aircraft to carry sufficient fuel to complete the entire sequence — destination, alternate (if required), and 45-minute reserve — from departure.
Sources
- 14 CFR 91.167 — Fuel Requirements for IFR Flight (Cornell LII)
- 14 CFR 91.169 — IFR Flight Plan: Information Required (Cornell LII)
- 14 CFR 91.103 — Preflight Action (Cornell LII)
- FAA Instrument Flying Handbook (FAA-H-8083-15B)
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This article was researched from FAA primary sources (14 CFR Part 91 via Cornell LII, Instrument Flying Handbook FAA-H-8083-15B) and citing current regulatory text — drafted by MockDPE. Last updated: May 2026. If you spot an inaccuracy, email corrections@mockdpe.org.
Frequently Asked Questions
What are the three fuel requirements under 14 CFR 91.167?
Under 14 CFR 91.167(a), you must carry enough fuel to: (1) reach the destination airport, (2) fly from the destination to the alternate airport if one is required, and (3) fly for 45 additional minutes at normal cruising speed. Helicopters substitute 30 minutes for the final reserve.
When is the alternate airport fuel not required under 91.167?
The alternate fuel leg is not required if the destination has a published instrument approach procedure and weather forecasts show a ceiling of at least 2,000 feet AGL and visibility of at least 3 statute miles from 1 hour before to 1 hour after your ETA. This is the (b) exception.
Does 14 CFR 91.167 apply to VFR flights?
No. Section 91.167 applies only to aircraft operated under IFR. VFR fuel requirements are governed by 14 CFR 91.151, which uses different daytime and nighttime fuel reserves.
What speed is used to calculate the 45-minute fuel reserve?
14 CFR 91.167(a)(3) specifies 'normal cruising speed.' This is the cruise power setting you plan to use for the flight, not maximum speed or published cruise charts. Use the speed you enter on your flight plan.
Do you have to file an alternate to satisfy 91.167?
Filing an alternate on the IFR flight plan (governed by 91.169) and carrying alternate fuel under 91.167 are related but separate requirements. If the (b) exception applies, you do not file an alternate and you do not need to carry fuel to reach one.
What ceiling and visibility numbers trigger the 91.167(b) exception?
For fixed-wing aircraft, the forecast must show a ceiling at least 2,000 feet above the airport elevation and visibility at least 3 statute miles for the period from 1 hour before to 1 hour after the ETA. Helicopters use 1,000 feet (or 400 feet above the lowest approach minimum, whichever is higher) and 2 statute miles.
What is the difference between 91.167 and 91.169?
14 CFR 91.167 defines how much fuel to carry for an IFR flight, including when alternate fuel is required. 14 CFR 91.169 defines when an alternate airport must be listed on the IFR flight plan and what weather minimums that alternate must meet for planning purposes.
Can I use fuel onboard before departure to meet 91.167?
No. The fuel must be on board at the point of departure. The regulation requires the aircraft to carry sufficient fuel to complete the entire sequence — destination, alternate (if required), and 45-minute reserve — from the point of departure.
AI-generated study aid — not an official source. This article was written entirely by AI working from FAA primary sources (Instrument Rating ACS, 14 CFR Part 91, Aeronautical Information Manual, Instrument Flying Handbook, and relevant Advisory Circulars), with sources cited inline so you can verify each claim. It has not been reviewed by a CFI, DPE, or other certificated aviation professional. AI can hallucinate, misstate section numbers, and subtly paraphrase regulations in ways that change their meaning. Treat this page as a study starting point only — always confirm any regulatory, procedural, or operational fact against the linked FAA primary document before relying on it for a checkride, a written exam, or a flight. Last updated May 17, 2026. Spotted an error? Email corrections@mockdpe.org.