Parece não haver regulamentações que requeiram emergência de emergência em caso de uso de combustível de reserva. O DoT dos EUA InFO 8004 discute especificamente isso:
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.
Notando que o piloto declarando combustível mínimo não é uma emergência,
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.
(ênfase minha)