Originally Posted by
meleagertoo
My understanding is that the FAA (among a number of other juristictions worldwide) does not officially recognise/adopt this phraseology. If this is indeed the case one can only wonder why, it's a extremely useful to be able to declare a level of urgency rather than an outright (by definition potentially life threatening) emergency.
Also specified in 7110.65, 10-1-1b:
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.