The grounding of all United Continental flights in the United States is coming to an end.

The flights were temporarily grounded this morning because of computer problems. Less than two hours later, United asked the Federal Aviation Administration to lift the ground stop order. And a passenger in San Francisco says passengers are again boarding planes.

United cited "network connectivity" as the source of the problems.

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 today.

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.