There are a number of options for traveling with your bike, but no matter what, the main goal is to keep your bike as safe as possible from the unknown things that happen once it passes the agent when you check in for your flight.
While there's the argument that you can pack your bike and fly with a cardboard box for cheap or free, and I've done that multiple times, it's still a big risk and many airlines won't compensate you if something happens to it. With a good bike specific case, you may not avoid the baggage fee but you're more likely to have your bike arrive intact and have an easier time rolling it around the airport.
RoundTrip Traveler Bag Details
• Fits most wheel sizes
• Fork mount with axle adapters
• Internal storage pockets for accessories
• Fits most standard MTB's, wheel sizes, and frame sizes
• Weight: 17 lbs
• Outer Dimensions: 51.5" x 14.75" x 32"
• Inner Dimensions: 50.75 x 14.5" x 31"
• MSRP: $479.95 USD
Thule have been making bike cases for quite some time now. While they still make the classic "hard case", they now have a couple soft-shell options that are easier to manage and travel with. The RoundTrip Traveler is the more basic of the two soft-shell options. The bike mounts directly into the case via the fork with whichever axle adapter you need, then it is tied down with several adjustable straps. There is an adjustable block that the bottom bracket sits on, and a strap that runs under it and over the chainstays.
The wheels fit in two zipped outer pockets, one on each side. The entire bag is lined with a durable material on the outside and inside, and the main compartment is lockable. There are handles on both ends and both sides, and small wheels so that the bag can be carried or rolled.
Plenty of adjustable straps keep your expensive pieces of plastic and metal where they should be.
Strap the bike in and off you go.
Packing my bike up before a trip was trouble free - the frame fit easily into the back, and the straps were simple to adjust, securing the bike to the bag, and bag to the bike. The fork mount is helpful in keeping the bike even more secure, although I did end up flipping the fork around backwards, but it was as painless as putting any bike into a bag could be.
29" wheels with 2.5" tires fit into the compartments, but it was pretty snug, and required partially deflating the tires. The accessory pockets on the inside were perfect for keeping a few zip ties, a multi-tool, pedals, plus the different adapters for forks axles. The wheel pockets have hard plastic pieces where the cassette and axles/brake rotors are to keep from damaging those. I typically don't fly with brake rotors on the wheels, just to be safe, but I decided to risk it this time, for the sake of "testing the bag" and was pleased to have no issue with them being bent either to or from my destination.
I've taken a few flights so far with the bag and it's easy to maneuver around the airport. The wheels roll well and are big enough to not get hung up on small stuff, and I can drag the bag through dirt and grass with ease. The handles on the bag are well placed and aplenty; there are two on each side of the bag, a couple on the front and back, with one on top for good measure.
When it's not in use, the bag can be collapsed by removing two hard pieces of plastic from the front and rear of the bag. The plastic pieces lay flat inside the bag and the bag can collapse - helpful if you're flying in somewhere and need to get the bag sized-down to fit in a car or your buddy's house while you're dirtbagging floor space on a riding trip.
Few things compare to the stress of watching a stranger toss your bike bag onto a luggage belt or slide it onto the baggage claim.
There are a couple of things that are worth noting, especially when you're spending almost $500 on a bike bag. The first is that some bikes will possibly be a bit long for the bag. With my size medium Yeti SB130, which is a fairly long 29er, I ended up turning the fork around backward and pulling the derailleur off. Although you don't necessarily have to pull the derailleur, I think it's a good idea and an easy way to prevent possible damage. Larger bikes that are a tighter fit may need to have some air let out of the fork to get the front end low enough, as with most bike bags.
I would also like to have seen some extra frame protection incorporated into the whole package. EVOC has a nice wrap that goes around the forward part of the front triangle to give a little extra protection from the handlebars or whatever else may bang against the frame. Something similar would be a good addition and personally, I have been wrapping that part of the bike with some extra to protection like a towel or some other riding gear.
29" wheels with 2.5" tires were a bit of a tight fit. I had to let most of the air out of them but not so much that I dislodged the bead and spilled sealant everywhere, which has happened before. If you're running a higher volume tire, be prepared to air down and then air back up again once you reach your destination, possibly having to re-set the bead if it burps - something that could take a trip to a local bike shop to use a compressor depending on your set-up or what pump you have.
It may be a tight fit with a long bike but take the derailleur off as you should and flip your fork around and you should be good to go in most situations.