Boy is this a tough one! There are various SCUBA magazines and online chat boards discussing all of the possibilities. In general, first you have to decide what will you need to take with you and what can you rent when you arrive (tanks are not generally worth carrying with you). Then you have to decide what you will pack in your carry-on bags and what you will check-in. Obviously you cannot carry onto the plane your SCUBA knife, bangstick, or spear gun. Keep in mind that the cabin is pressurized while the cargo hold is usually not. Some airlines do not approve of the SpareAir canisters while others will allow you to carry it onto the plane. In general you want to carry on your computers, regulators, lights, cameras, and BCD if possible. The rest of the equipment (weights, dive suits, mask, fin, snorkel, and armaments) should be checked. The last consideration is that most airlines charge an Excess Baggage Fee for SCUBA gear, regardless of the weight so that if you bring it in your fancy SCUBA bag you are announcing to the world that you have SCUBA gear inside. Best Bet: Call your airline or check their website before showing up at the airport.