IFR fuel requirements14 CFR 91.167 Fuel requirements for flight in IFR conditions
To fly in IFR conditions an aircraft must carry enough fuel to reach the first airport of intended landing, fly from there to the alternate airport, and then fly 45 more minutes at normal cruising speed (30 minutes for helicopters). The alternate leg drops out when the destination has a published instrument approach and the forecast meets the weather test in paragraph (b).
By the ATIS Alerts team · Updated October 15, 2026 · Regulation text current as of October 14, 2026. A study aid based on the official regulation text, not legal advice or an FAA interpretation.
At a glance
- Fuel to complete the flight to the first airport of intended landing (a)(1).
- Fuel to fly from that airport to the alternate airport, unless paragraph (b) applies (a)(2).
- Then 45 more minutes at normal cruising speed, or 30 minutes for helicopters (a)(3).
- The fuel figure must consider weather reports, forecasts and weather conditions (a).
- No alternate fuel for aircraft other than helicopters when the first airport of intended landing has a Part 97 standard instrument approach (or a special procedure issued to the operator) and, for at least 1 hour before and for 1 hour after the ETA, the ceiling is forecast at least 2,000 feet above airport elevation and the visibility at least 3 statute miles (b)(1) and (b)(2)(i).
- Helicopters skip the alternate fuel when, from the ETA to 1 hour after, the ceiling is at least 1,000 feet above airport elevation or 400 feet above the lowest applicable approach minima, whichever is higher, and the visibility is at least 2 statute miles (b)(2)(ii).
In plain English
Section 91.167 sets the minimum fuel for any flight in IFR conditions. It works in three legs: enough fuel to reach the first airport of intended landing, enough to continue from there to the alternate airport, and enough to fly 45 minutes after that at normal cruising speed. Helicopters need 30 minutes for the last leg instead of 45. The rule says the calculation must consider weather reports, forecasts and weather conditions, so forecast winds and weather belong in the plan, not just the distance.
The alternate leg in (a)(2) is not always required. Paragraph (b) removes it when two things are true. First, Part 97 prescribes a standard instrument approach procedure for the first airport of intended landing, or the FAA has issued the operator a special instrument approach procedure for it. Second, for aircraft other than helicopters, weather reports or forecasts indicate that for at least 1 hour before and for 1 hour after the estimated time of arrival the ceiling will be at least 2,000 feet above the airport elevation and the visibility at least 3 statute miles.
Helicopters have their own test in (b)(2)(ii): at the estimated time of arrival and for 1 hour after, a ceiling of at least 1,000 feet above the airport elevation or at least 400 feet above the lowest applicable approach minima, whichever is higher, and at least 2 statute miles visibility. Even when paragraph (b) removes the alternate leg, the reserve in (a)(3) still applies.
The same exemption wording appears in 91.169(b), which decides whether an IFR flight plan must list an alternate airport. Because the conditions match, a flight that fails the (b) test needs both an alternate on the flight plan and the fuel to reach it.
Common mistakes
- Counting the 45-minute reserve from the destination when an alternate is required. Under (a)(3) the reserve is flown after reaching the alternate.
- Checking the destination forecast only at the ETA. For airplanes, (b)(2)(i) covers at least 1 hour before and 1 hour after the estimated time of arrival.
- Forgetting the approach condition in (b)(1). Good weather alone does not remove the alternate fuel if the first airport of intended landing has no Part 97 standard instrument approach procedure (or special procedure issued to the operator).
- Reading the 2,000-foot ceiling as an MSL altitude. Paragraph (b)(2)(i) measures it above the airport elevation.
The official text
14 CFR 91.167 as published on the eCFR, current as of October 14, 2026.
(a) No person may operate a civil aircraft in IFR conditions unless it carries enough fuel (considering weather reports and forecasts and weather conditions) to—
(1) Complete the flight to the first airport of intended landing;
(2) Except as provided in paragraph (b) of this section, fly from that airport to the alternate airport; and
(3) Fly after that for 45 minutes at normal cruising speed or, for helicopters, fly after that for 30 minutes at normal cruising speed.
(b) Paragraph (a)(2) of this section does not apply if:
(1) Part 97 of this chapter prescribes a standard instrument approach procedure to, or a special instrument approach procedure has been issued by the Administrator to the operator for, the first airport of intended landing; and
(2) Appropriate weather reports or weather forecasts, or a combination of them, indicate the following:
(i) For aircraft other than helicopters. For at least 1 hour before and for 1 hour after the estimated time of arrival, the ceiling will be at least 2,000 feet above the airport elevation and the visibility will be at least 3 statute miles.
(ii) For helicopters. At the estimated time of arrival and for 1 hour after the estimated time of arrival, the ceiling will be at least 1,000 feet above the airport elevation, or at least 400 feet above the lowest applicable approach minima, whichever is higher, and the visibility will be at least 2 statute miles.
Test yourself
Practice questions from our free FAA written test prep that cite 14 CFR 91.167.
Instrument Rating
When an alternate is required, IFR fuel rules require enough fuel to fly to the destination, then to the alternate, plus:
- A. 45 minutes at normal cruising speed.
- B. 30 minutes at normal cruising speed.
- C. 60 minutes at normal cruising speed.
- D. no additional reserve.
Show answer
A. 45 minutes at normal cruising speed. 14 CFR 91.167 requires fuel to reach the destination, then the alternate airport (if one is required), and then 45 minutes at normal cruise beyond that.
More Instrument Rating practice →Instrument Ground Instructor
No alternate airport is required. The minimum fuel for an IFR flight in an airplane is enough to fly:
- A. to the first airport of intended landing, and after that for 45 minutes at normal cruising speed.
- B. to the destination plus 30 minutes at normal cruising speed.
- C. to the destination plus a 20 percent reserve.
- D. to the destination plus one hour at holding speed.
Show answer
A. to the first airport of intended landing, and after that for 45 minutes at normal cruising speed. The IFR reserve is 45 minutes at normal cruising speed; when an alternate is required, add the fuel to fly from the destination to that alternate first. The day-VFR 30-minute reserve is the classic wrong answer.
More Instrument Ground Instructor practice →CFII Helicopter
IFR fuel for a helicopter must cover the first airport of intended landing, then the alternate if one is required, and then:
- A. 30 minutes at normal cruising speed.
- B. 45 minutes at normal cruising speed.
- C. 1 hour at holding speed.
- D. 20 minutes at best-endurance speed.
Show answer
A. 30 minutes at normal cruising speed. Helicopters get a 30-minute final reserve where airplanes need 45. Teach it as a floor, not a plan: an IFR helicopter burns through options quickly once an approach goes missed.
More CFII Helicopter practice →
Questions pilots ask
How much fuel do I need for an IFR flight?
Enough to fly to the first airport of intended landing, then to the alternate airport, then 45 minutes more at normal cruising speed (91.167(a)). Helicopters need 30 minutes for the final reserve (a)(3). The alternate leg drops out when paragraph (b) is met.
When do I not need fuel for an alternate under IFR?
When the first airport of intended landing has a Part 97 standard instrument approach procedure (or a special one issued to the operator), and weather reports or forecasts indicate, for at least 1 hour before and for 1 hour after the ETA, a ceiling of at least 2,000 feet above the airport elevation and visibility of at least 3 statute miles (91.167(b)). Helicopters use the test in (b)(2)(ii). The 45-minute reserve in (a)(3) still applies.
Is the IFR fuel reserve 45 minutes at cruise or at holding speed?
The rule says 45 minutes at normal cruising speed, or 30 minutes at normal cruising speed for helicopters (91.167(a)(3)).