Nice not to need storing a box which can be a hassle and/or expense. never flown with a bike, the whole prospect gives me shivers. Am thinking about a tour in Germany (I live in the DC USA area) & while Munich airport, for instance, has storage that could accommodate a bike box, it costs about 7 euros/day. & if one has a different airport for the return flight that doesn't work. Bag or box, it seems that US airlines don't give a hoot about bikers & I'm not sure Euro/UK airlines are any better. If I had the $$ to spare I'd get a super-deluxe tourer with Rohloff & belt drive & couplers & fly with a hard case. I read that it's a bit difficult to fit a big touring bike with mudguards & racks & 559mm wheels (even with couplers) into a no-extra charge for bikes case but apparently it can be done.
Nevertheless the bag idea is intriguing. If one takes a little precaution, I suppose the worst damage one could usually expect is a bent rim although frame damage is a scary possibility. One could take a cab to a bike shop & buy a new wheel. BTW on my last trip to Germany I saw airline crew etc riding bikes around inside the airport terminal. Jeez, seems like the big airports could have some co-operative system to provide hard-shell bike cases for a reasonable fee.