What's Behind All These Airline Computer System Malfunctions?

We've seen it too many times in the past few years. Airline computer systems shut down leaving passengers stranded for days, resulting in massive revenue hits, ruined vacations, and lost productivity. What's behind this? American blamed SABRE, see below, when its reservation system crashed in 2015; United has cited various gremlins over the years for its computer malfunctions (2007, 2011, 2015) including "router failure"; Southwest (2015, 2016) faulted a "network equipment failure" and the subsequent failure of backup systems; and most recently Delta fingered the Atlanta power company for its crash, but turns out it was an issue with Delta's equipment ("Critical systems and network equipment didn't switch over to backups," the airline's COO was quoted as saying).

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