Also see here (Congress bill on airline handling), and here (airline stories)!
Accord – lightweight but expensive
Karura – still light, but a better price than the Accord
Calton – have always been strong, but heavy – new developments mean a lighter case
Hiscox – a lower cost alternative – make sure to get the flight case
Pegasus – the slim version might get your guitar on the plane, but padding is minimal
A canvas or cloth cover can make the case appear to be a soft one, which might increase your chances of getting it on board (paradoxically).