I'm sorry that your frame has been damaged, but from bitter experience I think most people are far too casual when packing their bikes for air travel. In a lot of cases it is the return flight where the damage happens. I think people are generally quite tired after their holiday and are more likely to make mistakes in packing their bike away.
Always assume the worst with baggage handlers, try not to give them an excuse.
1 Discs should never be attached to the wheel. They are an easy thing to damage by themselves when riding and if turned towards the frame in your bag/box there is potentially more metal to metal contact with the frame as well as them getting bent.
2) Pack with your cassette turned away from the frame.
3) Special attention should be taken with padding on your hubs. Wheels will generally overlap your frame and the hubs are the point of the wheel that will transfer the most force onto your frame if your bag is dropped. I have seen suitcase fall 10ft of the loading conveyor.
4) Don't try and squeeze everything in. Most bags can't take a 160mm or bigger fork. Take the fork off. Dismantle your bike as much as you can to fit into the bag/box with ease. Either take tools (any holiday worth it's salt should have at least enough workshop tools.
5) Pipe lagging is useless for modern frames. Sleeping mats from the likes of Tesco are easier to use and cheaper and if attached properly stay on to the parts you are trying to protect.
6) Dont' take risks, don't want to be too derogatory about baggage handlers, but why let them ruin your rather expensive holiday or pride and joy.
Good luck with chasing your claim