What does the AM mean in Trans AM?

What does crossing-code mean in a trans-oceanic flight?

• I was listening on Channel-9 in an UA flight to London, and there was an ATC controller asking for "What's your trans-oceanic crossing code tonight?" What is that code? And what else is different in an trans-oceanic flight?

• Answer:

  nope smooth, he was asking for the aircraft selcall code. a four letter code that the controller can signal when he needs to talk to the aircraft. this is done so that the crew does not have to monitor the noise from the hf radios that can't be gotten rid of. for instance our selcall was HBCA. the controler fires this code of and our selcall will chime alerting us to flip up our hf switches and we would then make the call "shanwick boeing six seven juliet romeo answering selcal hotel bravo charlie alpha". the controller would then tell us what he needs such as winds aloft check or often if we can reach an aircraft on vhf that he's been unable to contact that's in our area. the other things that are different over water besides the need for long range hf is the requirement for two long range nav systems. also it is a non radar invironment so five part position reporting is necessary. emergencies such as loss of pressurization take some different thinking too. there's more but those are the basics.