The computers, which handle data on items such as air pressure and temperature, recently underwent upgrades in which some steps needed to return the units to service weren’t completed or were performed out of sequence, Megan McCarthy, a spokeswoman, said today in a telephone interview.
All the affected computers have been working normally, she said. The work takes 60 to 90 minutes and began “immediately” when the Chicago-based parent of United and Continental airlines identified the issue earlier today, she said.
Passengers on certain United flights scheduled for tonight and tomorrow morning may face delays or cancellations, according to McCarthy, who said she didn’t have a total number. Continental’s Boeing 757s aren’t affected.
“This was voluntary by United,” a Federal Aviation Administration spokeswoman, Laura Brown, said in an interview.
The issue stems from an airworthiness directive from 2004, Brown said. The directive required that new circuit breakers, relays and related components be installed in air data computers on the 757, a twin-engine, single-aisle jet used by U.S. carriers on domestic and international routes. Chicago-based Boeing ended 23 years of production of the model in 2005.
Some United 757s may be in flight right now, and the checks will be done as soon as the planes land, McCarthy said at about 6:30 p.m. New York time. Other jets are being checked by maintenance crews that are on site before they depart, she said.
United Continental was formed by the merger of United parent UAL Corp. and Continental Airlines Inc. in an all-stock deal in October, creating the world’s largest carrier.