"Our system is up. We're resuming operations for affected flights," the airline said in a tweet at 10:52 a.m. EST (1552 GMT). Approximately 30 minutes earlier, the airline had tweeted that a computer problem was affecting some flights, but did not indicate how many.

Company representatives were not immediately available to comment on the extent of the problems. There was no information on the situation posted on the web page where United updates its operational status.

Live flight status information for Denver International Airport showed delays for nearly 30 flights of United's scheduled morning departures. Houston's Intercontinental Airport and Newark Liberty Airport in New Jersey, showed delays of a few minutes in length, though not as many as Denver.

All three airports are hubs for the airline.

Shares in the company fell 1 percent to $19.79 in morning trading, having regained some ground after reporting that the computer problems were resolved.

In August, a temporary network outage hampered United's website and airport functions, causing flight delays and cancellations. As a result, United said it allowed passengers affected by the incident to cancel and rebook flights without penalty.

United bought Continental in a $3.17 billion stock deal in 2010, creating the world's largest air carrier. The merged company has had problems integrating operations.

In March, United adopted Continental's reservation system, triggering computer glitches that caused flight delays, faulty kiosks and jammed phone lines. (Reporting by Ben Berkowitz; Editing by Jeffrey Benkoe)

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