A computer malfunction at United Airlines halted all departures systemwide for two hours Wednesday, forcing the delay or cancellation of nearly 300 flights, the carrier said.  Spokeswoman Robin Urbanski said the airline did not know the cause of the problem, which affected the systems United uses to dispatch flights for departure.

United said about 268 domestic and international flights were delayed for an average 11/2 hours and 24 domestic flights were canceled. No international flights were canceled, Urbanski said.