Aging technology, human error, and complex systems are to blame.
A Delta plane at the airport.
Credit: Getty Images

The power outage that grounded more than 1,000 Delta Airlines flights Monday and continues to affect even more flights, is just the latest in a series of troubles resulting from the industry’s antiquated computer systems.

Last month, a computer glitch grounded 1,000 Southwest Airlines flights while United had an issue with a router that caused global delays for two hours. JetBlue has had two major tech upsets this year: In January, a power failure at one of its Verizon-run data centers caused major flight delays, and in May, the airline had to rely on old fashioned methods of manual check-in after a system-wide computer outage.

Why the increased onslaught of IT failure?

Most airlines have not fully updated their technology systems in decades, focusing on a more urgent need to merge their aging systems as the industry has consolidated. That means no two airline systems are alike and each come with their own built-in problems. Some airlines, like Southwest, have two different systems to keep track of domestic and international bookings.

It’s complicated

An airline’s “system” is a complex series of networks that perform many different functions: reservations, ticketing, checked baggage, and real-time flight status, for starters. Each airline maintains a database of info for all of its customers, including their credit card numbers and personal data.

The system also must connect with a global airfare pricing network to update fluctuating prices that are based on ever-changing supply and demand. Everyone hates cancelled flights, but no one complains when a technical glitch offers roundtrip airfare to Bora Bora for $1.

Airlines also must communicate with the U.S. government’s security databases, such as the No Fly List. All of those layers of networks require additional security to prevent hackers from wreaking havoc.

Because of the antiquated technology that is used to connect those many layers, an outage can have a domino effect, resulting in a complete system shutdown, especially if there’s no emergency backup power supply. Many airlines, including Delta, have been slowly modernizing their networks, but experts have said the updates have been done incrementally—and are very expensive.

Did a power outage really cause a disruption in service?

Airlines usually have a failsafe power supply system in the event of an emergency. Experts and flyers have been quick to blame other factors, such as human error, and potentially hackers, though Delta has not commented further. Almost 12 hours after yesterday’s power failure, Delta posted a video apology from CEO Ed Bastian. Tuesday morning, the company said it anticipated more delays, and cancelled more than 300 flights.

As one expert told CNNMoney: “Somehow, someone created a threat in the Delta Air Line situation that caused their disaster recovery not to work. How do I know it? Because their disaster recovery system should have worked. And it didn't.”

Delta passengers who have been impacted by the outage should review the airline’s website for updates.

Christopher Tkaczyk is the Senior News Editor at Travel + Leisure. Follow him on Twitter and Instagram at @ctkaczyk.