the bottom line is that the science of decompression is all theory. most of it is good theory, but it is theory none the less. how a dive profile affects you today may not be how it affects you tomorrow. and it may affect your buddy differently as well.
as soon as i hear people saying "well you should be ok", or handing out advise as if the diver is a highly trained navy seal, i say maybe you should rethink what you are doing.
i have a standard line i use at work when i am training new technicians. if you have to ask whether you should be doing something or not, you have already aswered your own question.
my advise is to always err on the side of caution, and remember that the guidleines used by training agencies and by DAN are "minimum" standards. i would hope we all would want to try and exceed any minimum standards.
i know instructors that won't fly for 24 hrs after spending an hour or two in the pool.
that said, an otherwise healthy and fit diver, completing two dives within the NDL (you came fairly close on dive one) would be following minimum guidelines if they flew after 18 hours. this is assuming you are on a typical pressurized commercial flight, which you were not. so in the end it is your call.
i would ask....were you the pilot or the passenger? i would be curious to know what the pilots guidelines are. i have taught a couple of bush pilots and i know they have to follow a different set of rules.