I think a disabled person has just as much right to travel as anyone else. Having to call beforehand, while easy, shouldn't be required. I think that limiting the number on an aircraft should also not be a requirement, unless the number is reasonable. (9 is too low). Signing away our lives so an airline can just leave us in an emergency is the wrong approach. Everyone who boards an aircraft assumes the risk of a crash. Disabled people either have to take the risk, or stay home, signing a paper is not necessary.

An airline, must be responsible for the people it transports. Discriminating should not be allowed. If the airline can't handle it, maybe they shouldn't be in the transport business.