RACHEL MARTIN, HOST:
United Airlines expects operations to be back to normal today after a computer glitch grounded all domestic flights for a few hours on Sunday night. That delayed thousands of travelers. Many of them missed their connecting flights. NPR's David Schaper reports many airlines seem to be struggling with their technology these days.
DAVID SCHAPER, BYLINE: Dan Micheli arrived at Denver International Airport Sunday evening a little early for his 7:05 flight to Phoenix. He checked his United app and information screens at the terminal, which showed that his flight was on time. But as he walked through the concourse to his gate, he saw it was flooded with people.
DAN MICHELI: Yeah, I noticed quite a bit of crowding and a lot of people at a lot of gates - got to my gate and saw that the earlier flight had not yet left.
SCHAPER: That flight was supposed to take off two hours earlier. The gate agent said it was a computer problem, which for Micheli, who flies every week on business, immediately raises questions.
MICHELI: Where's the redundancy? Where's the resiliency that ensures that a system like that is always up and always ready?
SCHAPER: In a statement, United says an IT issue prevented pilots from getting certain information they needed to take off, like the weight and balance of the aircraft to calculate speed. Experts say the problem likely involved the ACARS system, which transmits data between the aircraft and the airline's operation center.
AHMED ABDELGHANY: ACARS are very important systems for the airline operation.
SCHAPER: Ahmed Abdelghany is a professor of airline operations management at Embry-Riddle Aeronautical University.
ABDELGHANY: Typically, systems like that, it should be working 24/7 supporting all the flights. And the problems are not expected to happen.
SCHAPER: United says the problem was resolved within two and a half hours Sunday night. But Abdelghany and others note that there have been several technology problems at United and at other airlines in recent months - one outage bringing down Delta's systems for two days last summer, another forced Southwest to cancel flights for days, too.
Daniel Baker is CEO of the flight tracking service flightaware.com.
DANIEL BAKER: The big problem that airlines face is that a lot of these are legacy systems, meaning they've been around for decades. And the demands on them are getting greater and greater.
SCHAPER: These are huge, complex systems. And every airline's is different, which has created more complications as the airlines have merged.
BAKER: Now they have an even bigger system on top that's relying on the same somewhat antiquated infrastructure.
SCHAPER: Airlines are posting big profits these days. And Baker says they're investing some of that money into IT upgrades. Passengers can only hope that airlines step that up to help prevent the kinds of technology problems that delay and cancel their flights. David Schaper, NPR News, Chicago. Transcript provided by NPR, Copyright NPR.
