Thanks for everyone's input.

I need to emphasize that the airline should be responsible for the mechenical problems. This can be an excuse but can not be accepted. For example, I am passenger and I need to arrive at the ariport on time. What if something happened to me right before the arrival to the airport? Say if the traffic jam or serious illness? Can the airline refund me the airfare without charging me? No. Everyone can make up some excuse for missing the flight.