By Mira Oberman
A computer glitch has grounded United Airlines flights for the second time in six weeks, backing up thousands of passengers in the busy morning travel rush.
The Wednesday morning (local time) glitch came shortly before trading was halted on the New York Stock Exchange as a result of technical problems.
While the timing of the two incidents raised concerns that a cyberattack was in progress, it appeared to be a coincidence.
There are "no signs of malicious activity at this time," a spokesman for the Department of Homeland Security told AFP, adding: "We're still investigating."
United flights around the country were prevented from taking off for more than an hour because "an issue with a router degraded network connectivity for various applications," the airline said.
"We fixed the router issue, which is enabling us to restore normal functions," United said in a statement.
About 900 flights had been affected by midday (local time) and more were expected to be delayed as United worked through the logistics, said Mark Duell, vice president of operations at FlightAware.com, which tracks flights and delays.
It will take hours, if not days, for the cascading delays to work their way through the system.
Because United is so efficient when it comes to turning their planes around, any significant delay can cause major disruptions.
Flights get backed up on the tarmac because delayed planes are still at the gate, connections get missed and crew members have to be replaced.