United Airlines ground stop lifted after computer issues

United Airlines said it was restoring flight operations after grounding all U.S. flights for nearly two hours today because of "network connectivity" problems.

The Federal Aviation Administration confirmed that the "automation issues" that had caused the ground stop have been resolved.

United tweeted a statement saying it is recovering from the computer glitch and will give waivers to passengers who have to rebook their flights.

At several major U.S. airports Wednesday, United boards showing departures and arrivals went blank during the ground stop, and ticket agents reportedly had to resort to pen and paper to check in passengers and baggage. Frustrated passengers shared photos on Twitter of long lines and crowded airports.

The outage lasted less than two hours.

Chicago radio station WGN reported the ground stop did not affect United's regional carrier, United Express.

Pearson International Airport in Toronto was advising passengers to check their flight status because of potential knock-on effects of the network issue.

An industry analyst said the grounding will frustrate Air Canada passengers travelling on shared flights with United but have little lasting impact on United or its Canadian partner.

"The next time you book a flight, you probably will remember it, but you're going to most likely look for the cheapest fare or the best connection. That's going to be a minor consideration," said David Tyerman of Canaccord Genuity.

Tyerman said there should be no impact on WestJet unless passengers are able to switch from United to the Calgary carrier.

United is a Chicago-based carrier that is the third largest U.S. airline in terms of market share, controlling about 15 per cent of the domestic market.

The airline briefly grounded U.S. flights on June 2, also because of "automation issues," in a move that lasted for less than an hour.

It 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. A number of high-paying business travellers defected to other airlines and revenue dropped.

"We don't know everything behind this morning's issues yet, but today's incident underscores the sense that something is very wrong at United," said Gary Leff, co-founder of frequent-flier website MilePoint.

Shares of United Continental Holdings Inc. slid two per cent to $53.08 US in early-morning trading.