In reply to Bonj's advice, drawn from his vast experience.....where do you leave your expensive hard case?
Airports. I work at one. Each airline, with the exception here of BA, who have their own, employ the services of a handling aent, a company like Aviance, Servisair, Groundstar etc. These companies employ the baggage handlers that take your kit to the plane, load it, and the reverse on arrival.
The etiquette is that backs are not bent, so bags are dropped from a great height onto the belt. Big flat things like bike boxes are handy for piling things on.
If a bike is in a CTC style clear plastic bag, it is recognisable as a bike and should be OK, which is why I have seen piles of such bikes--literally, piles four, five six high---at handling agents' desks.
In short, though I have met O'Leary many times, and he is a daffodil, the main causes for damage to your bike are outwith the airline. The excessive charges and odious conditions. however, are simply because O'Leary is a money-grubbing daffodil.