American Airlines briefly grounded flights nationwide on Tuesday due to a technical issue just as the Christmas travel season kicks into high gear. American flights were cleared to fly by federal regulators about one hour after a national ground stop order was issued by federal regulators.Just before 7 a.m. Eastern time, the Federal Aviation Administration ordered all American Airlines flights grounded in the US at the airline’s request. American had reported a technical issue affecting its entire system with millions travelling for the holiday.The ground stop, according to the time stamps on the FAA’s orders, lasted exactly one hour.American has not expanded on what technical issue grounded the flights and the airline did not immediately respond to a request for comment.The groundings couldn’t come at a worse time for the millions of travellers expected to fly over the next 10 days. The Transportation Security Administration expects to screen 40 million passengers over the holidays and through January 2.Many flights during the holidays are sold out, which makes cancellations even more disruptive than during slower periods. Even with just a brief outage, the cancellations have a cascading effect that can take days to clear up.In December 2022, Southwest Airlines stranded 2 million travellers, and Delta Air Lines suffered a smaller but significant meltdown after a worldwide technology outage in July caused by a faulty software update from cybersecurity company CrowdStrike.Southwest was ordered to pay a USD 35 million fine as part of a USD 140 million settlement to resolve a federal investigation into the Christmas debacle of 2022.Excluding the settlement, the nation’s fourth-biggest airline by revenue said the meltdown cost it more than USD 1.1 billion in refunds and reimbursements, extra costs and lost ticket sales over several months.