My 1/96 Blueback travels in an arrow case. Room enough in there for the boat and transmitter, stand, and a couple extra batteries. Fits in the overhead just fine.
I've also used in the past a length of PVC pipe, both split to make an opening case, and left round with end caps.
Other than the funny looks you get, no problems. A few suggestions:
1. If you have a gas boat, remove the valve core from the ballast filler. Do NOT carry Propel thru security at the airport.
2. Let the folks at the scanner know you have an R/C model in the case before they run it thru the x-ray. This cuts down on the "excitement" factor.
3. Carry an old issue of the SCR, just in case they get really curious about you being legit.
Underwater, the ONLY way to fly!
SubCommittee member #0069 (since the dawn of time)