It seems like a new major airline cancels flights due to computers crashing about once or twice a month anymore. Delta Airlines suffered from an IT outage at the end of January and just a week before United Continental struggled with issues with their communication system.
Others have seen the same issues over the past few years including Southwest Airlines and Delta last summer. Delta took a $150 million hit last August and the four-day issue from Southwest cost them about $54 million.
These issues have many major airlines investing hundreds of millions of dollars in IT security. Many are asking IT professionals to make their system bullet-proof with fail-over redundancy.