United Airlines halted takeoffs nationwide Wednesday morning because of a computer breakdown, the second time since June that the company has taken such a step. The delay does not appear to have affected planes that were already aloft. From CNN:
The problem started shortly before 9 a.m. ET, and affected both United and the feeder airlines that fly under names such as United Express. By 9:20 a.m., the feeder airlines were released from the ground stop, according to the FAA, but the United flights were still grounded.
"Automation" issues were responsible, the FAA said; per the tech site The Verge, that's "another way of saying that United is having trouble with the back-end software and hardware that it uses to coordinate flights at the several hundred airports it serves."
At least some of the carrier's pilots appear to have handled the situation well:
United has had similar problems in past years. From Bloomberg:
In February 2014, the system that handles check-ins and other passenger services failed, disrupting travel for about three hours at United hub airports including San Francisco, Washington and Chicago. The previous month, a malfunction stranded pilots and caused about 1,500 cancellations.
United added extra precautions in 2012 after a computer breakdown caused one of its planes to take off about 20,000 pounds (9,100 kilograms) heavier than pilots believed, creating difficulties in getting the jetliner airborne.
Nate Silver's 538 site reported in June that United flights were delayed more, on average, than those of any other airline during the 12 most recent months for which data was available.