Essentially, the baggage handers carry your board by the Handle, on the Boardbag...

The boards get thrown into containers, by guys who don't know how fragile they can be... these guys don't surf... They see the padding on your boardbag, and assume the boards become indestructible inside the Padded Board Bag.

Take a Tufflite, or;

Take "duct tape" along... Tape on foam padding blocks onto the tail and the nose. (or a fabricated 'shoe' of bubble wrap).. and also put a good layer of foam or 3-4 layers of bubble wrap onto the rail that is opposite the carry handle. The board gets dropped onto this rail... Secure the bubble wrap into position with the duct tape.

Or just wrap your wettie and towels around the rails and duct tape in position to protect the rails. As Simondo points out the one opp. the handle the most important. I also normally put shoes around the nose - each side - on the short boards and a bunch of clothing around the tails. When I head off on a surf trip I normally just take a 3 * board bag with 2 boards in it and all my crap. I normally put the boards in a light day bag as well so heaps of protection. Never had any issues thank goodness.