An as-yet-unidentified computer failure grounded all departing United Airlines flights on Wednesday morning.

The two hour glitch was confined to the carrier, but caused chaos across US airports as arriving planes were stuck on the tarmac waiting for gates - occupied by United flights that weren't moving anywhere - to become available.

Problems persisted between 0800 and 1000 CDT, when systems were restored and planes were able to depart. "We were experiencing a computer outage and now our computers are back up," United spokeswoman Robin Urbanski told AP. "Right now we're working hard to resume our operations."

United has apologised to passengers for delays caused by the incident, which reports suggest involved failures in the computer system used to match fuel with passenger load. ®

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