An airport is not a good place to try.
If the guy doesn't like it, he will feel even more refrained from returning it, since there's a ton of people all around.
If he doesn't like it but pitties you so much he does return the salute, he will feel bad for having done it with a ton of people all around and you'll be guilty of this, you evil monster.
That's it.
I'd include the third option of the guy liking it and happily returning it for all to see, but I've since learned that in Subsim we are supposed to deliberately cut off the options that don't suit our case and present only those that do.
I've never saluted a soldier, but I do stop them whenever I can to praise them.