For info, no mention of PAN but .....
Extract from UK CAA CAP493 Manual of Air Traffic Services Part 1:
Fuel Shortage
4.41 Controllers are not required to provide priority to pilots of aircraft that
have indicated or suggested that they are becoming short of fuel
or have used the RTF Phraseology “MINIMUM FUEL”. The term
MINIMUM FUEL indicates that the pilot, having committed to land at a
specific aerodrome, calculates that any change to the existing clearance
to that aerodrome may result in landing with less than the planned final
reserve fuel.
4.42 Controllers shall respond to pilots who indicate or suggest that they
are becoming short of fuel or who have declared “MINIMUM FUEL”
by asking the pilot to confirm whether or not he wishes to declare
an emergency after confirming to the pilot, the estimated delay he
can expect to receive expressed in minutes, if the pilot is en-route
to, is joining, or is established in an airborne hold, or by expressing
the remaining track mileage from touchdown, if the aircraft is being
vectored to an approach.
4.43 Once in possession of either the estimated delay or remaining track
mileage, pilots will determine whether or not they should declare
an emergency. Pilots declaring an emergency will either respond
affirmatively or use the following RTF phraseology “MAYDAY, MAYDAY,
MAYDAY” or “MAYDAY, MAYDAY, MAYDAY FUEL” and controllers shall
provide such aircraft with flight priority category A. The term “MAYDAY MAYDAY MAYDAY FUEL” indicates that the pilot calculates the usable
fuel predicted to be available upon landing at the nearest aerodrome
where a safe landing can be made is less than the planned final reserve
fuel.