L.M.
I would suggest that you speak to your BIL in private and ask him why he would miss the appt to fly knowing it was already paid for (by you) for he and his brother to fly together since it was what his brother/your husband wanted for his birthday. Not that anything he says will be good enough but it will let him know you are unhappy and he was insensitive/inconsiderate. Mention that since you paid for his trip and the helicopter ride you definately feel that since he chose to miss it due to doing his own thing and thus hindering your ability to give your husband the gift you intended, you feel he should at least reimburse you for his portion of the ride.
Then let it go...he's your BIL and life will be easier on you and your hubby if you do.
ADDED...not attending or showing up to his brothers wedding is very immature and doesn't solve or change anything. It also makes things worse and means you're stooping to his brother's level.