Fuel Reserves Approaching Minimum
’Fuel Emergency’ or ‘fuel priority’ are not recognised terms. Flight crews
short of fuel must declare a PAN or MAYDAY to be sure of being given the
appropriate priority
source ICAO phrasology guide
Another area where FAA differs from ICAO. Here, we have "minimum fuel" and "fuel emergency", without a MAYDAY or PAN call required, being a recognized, sanctioned term. (
http://www.faa.gov/other_visit/aviat.../info08004.pdf ).
Note: Use of the term “minimum fuel” indicates recognition by a pilot that his/her fuel
supply has reached a state where, upon reaching destination, he/she cannot accept any
undue delay. This is not an emergency situation but merely an advisory that indicates an
emergency situation is possible should any undue delay occur. A minimum fuel advisory
does not imply a need for traffic priority
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 intended landing due to low fuel. Declaration
of a fuel emergency is an explicit statement that priority handling by ATC is both
required and expected.