ICAO
5.3.1.1 Distress and urgency traffic shall comprise all radiotelephony messages relative to the distress and urgency conditions respectively. Distress and urgency conditions are defined as:
a) Distress: a condition of being threatened by serious and/or imminent danger and of requiring immediate assistance.
b) Urgency: a condition concerning the safety of an aircraft or other vehicle, or of some person on board or within sight, but which does not require immediate assistance.
5.3.1.2 The radiotelephony distress signal MAYDAY and the radiotelephony urgency signal PAN PAN shall be used at the commencement of the first distress and urgency communication respectively.
IMHO, given the above, it's a line call either way but this is not the issue at hand. It's how two separate airlines end up landing at a regional airport on a runway ill equipped for the actual weather conditions.
That it happened to two separate crews from separate airlines points to a bigger issue than the actions of either flight crew; that it is a systemic issue in the regulatory culture is the most obvious culprit. Debating the RT actions of either crew is pointless here.
Last edited by compressor stall; 30th Jun 2013 at 10:28.