Lady and gentlemen is more my time, boys and girl is about right and the modern usage of "Guys" as a collective noun makes me vomit! It is even used by the BEEB during news bulletins.
Certainly these pilots have done a very different course to the one I instructed on at Valley in Gnats (64 to 66)! Well done and safe flying, have fun too BTW!
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It isn't a collective noun, its the plural of a common noun.
It's usage is informal, inclusive and friendly.
Suggest you put away the sickbag, listen to how people are speaking and try to understand what they mean.
Good luck and good flying to the graduates!
Rgds SOS