… But in recent years, the most frequent cause of software breakdowns is mergers.

“When airlines switch computer systems, you can bet on major problems,” says Boyd. “Sometimes for days.”

The most recent merger-related failure was caused when United Airlines adopted Continental’s software after the companies joined forces last year. Despite months of pre-planning and employee training, the “cutover” (the process of consolidating the two IT systems) resulted in technical issues that surfaced at airports across the country. Twitter feeds lit up with horror stories of bungled bags, ultra-slow check-ins and malfunctioning kiosks as United’s geek-squad worked through the weekend to fix the system.