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In another question, I wrote

You only need to plan for regulatory reserves. You don't actually have to land with them

and @Jan replied:

you have to declare emergency if you do cut into them though and that will quite probably get you an investigation

I have never heard that you must declare an emergency if you cut into your reserves (regardless of the stage of flight), and I'm wondering if there is any regulation to back it up.

The only reg that I could find that comes close is NTSB 830, which lists a set of criteria for notifying the NTSB within 10 days:

(a) An aircraft accident or any of the following listed serious incidents occur:

(1) Flight control system malfunction or failure;

(2) Inability of any required flight crew member to perform normal flight duties as a result of injury or illness;

(3) Failure of any internal turbine engine component that results in the escape of debris other than out the exhaust path;

(4) In-flight fire;

(5) Aircraft collision in flight;

(6) Damage to property, other than the aircraft, estimated to exceed $25,000 for repair (including materials and labor) or fair market value in the event of total loss, whichever is less.

(7) For large multiengine aircraft (more than 12,500 pounds maximum certificated takeoff weight): (a bunch of other things)

I'm interested in the answer for Parts 91, 135, and 121, under FAA regulations.

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if you cut into your reserves while lining up for the runway it's not useful to declare fuel shortage. If you miss the approach then it is useful to get the priority the emergency gives you. – ratchet freak Feb 1 at 12:28
I am not aware of anything that would require you to declare an emergency for fuel reserves. For that matter, I'm not aware of anything that would require you, strictly speaking, to declare an emergency in any circumstance. – Jonathan Walters Feb 1 at 12:40
Speaking from the standpoint of one who retired in 1999, if I had declared a fuel emergency every time I cut into the 45 minute reserve normally required back then for an IFR reserve, I would have been declaring an emergency on a regular basis. A fuel emergency, at least back then, was declared only if you thought you were going to run out of fuel if you didn't get priority handling. I never declared such, and to the best of my knowledge, I never landed without enough fuel to do a go-around and then circuit the field for a landing. – Terry Feb 1 at 13:07
I don't think it's regulation but I do believe some airlines have the SOP to declare emergency if you can no longer make the runway without cutting into your reserves. I have no source for that though. – falstro Feb 1 at 13:36
My PPL instructor told me that its not necessarily an emergency, but you better have a good explanation ready if you get ramp checked. Declaring an emergency is always a judgement call by the pilot, if you feel that you need extra resources or attention to get your aircraft safely on the ground, then declare. Otherwise you can always use the Aviation Safety Reporting System (ASRS) and be somewhat covered if somebody at the FBO reports you. – Ron Beyer Feb 1 at 14:38

There seems to be no regulations that require decleration of emergency in case of using reserve fuel. US DoT InFO 8004 specifically discusses this:

Emergency Fuel. Although not defined in the AIM or Federal aviation regulations, the industry-wide connotation typically associated with the term “Fuel Emergency” is:

The point at which, in the judgment of the pilot-in-command, it is necessary to proceed directly to the airport of in tended landing due to low fuel. Declaration of a fuel emergency is an explicit statement that priority handling by ATC is both required and expected.

Noting that pilot declaring minimum fuel is not an emergency,

The act of using a portion of the reserve fuel assigned to a flight is not, in its self a cause to declare a minimum fuel state with the controlling agency. Regulations require reserve fuel to enable aircraft to maneuver, due to unforeseen circumstances. Many aircraft safely arrive at their destination having used a portion of the fuel designated as reserve. There is no regulatory definition as to when, specifically, a pilot must declare “minimum fuel” or a fuel emergency. Air carriers typically develop such guidance for their pilots and include it in their General Operations Manuals; such guidance generally falls along the following lines:

•Declare “minimum fuel” when, in your best judgment, any additional delay will cause you to burn into your reserve fuel.

•Declare a fuel emergency at the point at which, in your judgment, it is necessary for you to proceed directly to the airport at which you intend to land. Declaration of a fuel emergency is an explicit statement that priority handling by ATC is necessary and expected.

(Emphasis mine)

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No, you don't, but per the AIM you should declare an emergency if you need priority for landing.

There may be some confusion here between declaring "minimum fuel" to ATC, and declaring an emergency. The AIM 5-5-15 says:

  1. Advise ATC of your minimum fuel status when your fuel supply has reached a state where, upon reaching destination, you cannot accept any undue delay.
  2. Be aware this is not an emergency situation, but merely an advisory that indicates an emergency situation is possible should any undue delay occur.


  1. If the remaining usable fuel supply suggests the need for traffic priority to ensure a safe landing, you should declare an emergency due to low fuel and report fuel remaining in minutes.

But in general there's no regulation or rule that I can find that says when a pilot must declare an emergency. The general guidance from the AIM 6-1-2 is that pilots are expected to declare an emergency when a state of distress exists. The ATC orders 10-1-1 are a little more specific:

A pilot who encounters a Distress condition should declare an emergency by beginning the initial communication with the word “Mayday,” preferably repeated three times. For an Urgency condition, the word “Pan-Pan” should be used in the same manner.

As for what distress actually means, the Pilot/Controller Glossary simply says:

DISTRESS− A condition of being threatened by serious and/or imminent danger and of requiring immediate assistance.

It's unlikely that cutting into fuel reserves by itself would constitute a "serious or imminent danger" (which is why "minimum fuel" isn't an emergency) but on the other hand if the pilot is also unsure of his position or has other issues to deal with, then it might still be the best thing to do.

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