The reason outages affect airlines more obviously than other businesses is because of the redundancies. Airline's won't operate without redundancies in place, which means if something goes out and the systems are taken to backup, that is considered a complete outage. An outage may only take down part of a system, but for safety reasons an airline isn't going to fly planes that they can't track, or dispatch a flight without an accurate copy of the manifest. It's easy to say that a few redundancies would fix the problem, but it's really not that simple (and lets be clear, two system failures does not a crisis make, even if they're close together). A small IT company really can't be compared to a global network of mobile systems that sends those systems 30,000 feet into the air, often over oceans, with hundreds of souls onboard.
Ask yourself this: do you really want to get on an airplane if the airline says, "Eh, that's close enough. We have most of the information". Answer: you don't.
Always nice to hear after I just worked 3 hours past the end of my shift to make sure that passengers got to their destinations after a cancellation.