United Airlines flights were grounded for nearly two hours nationwide Wednesday morning.
The Federal Aviation Administration issued a ground stop for all United Continental flights due to an "automation issue." The ground stop was lifted around 9 a.m. CT but delays were expected.
"We are recovering from a network connectivity issue this morning and restoring regular flight operations," United Airlines said in a statement. "We will have a waiver available at united.com for customers who are able to change their flight plans."
The airline blamed an "issue with a router" for the cause of the glitch.
"An issue with a router degraded network connectivity for various applications, causing this morning’s operational disruption," the airline said in a statement. "We fixed the router issue, which is enabling us to restore normal functions."
O'Hare International Airport reported delays averaging 15 to 20 minutes Wednesday morning. It was not immediately clear how many flights and passengers were affected nationwide.
Several passengers took to Twitter to express frustration on the issue.
It is the second time in two months that the carrier has been hit by major technical issues.
The Chicago company had halted all takeoffs in the U.S. on June 2 due to what the airline described as computer automation issues.
The Federal Aviation Administration used the same language in its notice about the outage Wednesday.
United suffered a series of computer problems in 2012 after switching to a passenger information computer system previously used by merger partner Continental Airlines.
In each case, hundreds of flights were delayed. A number of high-paying business travelers defected to other airlines and revenue dropped.
"We don't know everything behind this morning's issues yet, but today's incident underscores the sense that something is very wrong at United," said Gary Leff, co-founder of frequent-flier website MilePoint.
Shares of United Continental Holdings Inc. slid 2 percent to $53.08 in early morning trading.
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