The AIRE Kayak Bag runs $99 and can be used for air transport. It has just enough mesh along the top center between the lift handles to allow your kayak to dry somewhat, but none of this mesh is exposed in such a way that it will get torn by airport baggage systems. It measures 47" long by 15" around. In other words, it is cylinder shaped. This is a big bag that will carry any tandem boat except a Traveler canoe, and if your kayak is a solo or smaller tandem model you can also stuff paddles, pump, and maybe a lifejacket or two in there. The Kayak Bag has a long removable shoulder strap as well as two regular lift handles. Additionally, there are also two pockets on the inside, and two more on the outside.
The last feature of the Kayak Bag is a dubious pair of backpack straps on the bottom/rear side. These have a design flaw in that they connect to the bag's D-rings with plastic hooks, which can and do break. In fact, we have had customers break them on the very first use. If the backpack straps are a crucial feature for you, we would suggest trying to stuff your boat into a 3.8 River Pack (see our Dry storage page) instead. It will poke up out of the River Pack bag, but we have to assume anyone carrying their boat this way is hiking to a put-in, not carrying it to baggage check-in at an airport. If you are in an airport, better to use a luggage cart. If you do buy the Kayak Bag and the hooks break, understand that you have been warned and we will not take returns if this occurs. Even if the hooks didn't break so easily, the shoulder straps are hideously uncomfortable. Beyond the crabbing about this one detail, AIRE's Kayak Bag is a very nice product in every other way.
There is also a product AIRE has called the Deluxe Padded Boat Bag, but at almost 57" long, it is a rather ungainly size. We can special order it if you wish, and it runs $159 with a lead time of three business days. It is our opinion that a genuine U.S. military surplus duffel, perhaps with a bit of padding on the inside via sleeping pad material, is also a good way to go without spending huge amounts.