Or is there a difference between the Guard frequency used by US civil airliners and that used by NATO?? I'm sure there isnt.
Well actually, yes there is. Civilian guard frequncy is VHF, 121.5 whereas the NATO guard frequency is UHF, 243.0.
However, if you were asking if there was a difference between the civilian guard (VHF) frequencies between the US and the rest of the NATO nations, or the rest of the world, then the answer would indeed be no. 121.5 is the International Civil Aviation Authority (ICAO) guard frequency.
MadMark!!!