gooday from downunder. in reply to what happens on the continent and beyond it does come down to an understanding between the crew and atc which is easier to manage if english is the common language. A mayday is used when an aircraft is in grave and imminent danger and a pan for anything less than a mayday but still requiring assistance. Both forms of emergency( priority) require ( if possible) for the a/c to state the nature of distress(mayday) or urgency(pan) which is the time to state fuel emergency and an indication of how urgent your need to approach is.There are no published guidelines as to how much fuel remaining constitutes an emergency or urgency, that is a question of how much pucker your arse is suffering. There will always be much less embarrassment in filling out an incident report than facing a post crash media flock.