WASHINGTON — American Airlines briefly grounded flights nationwide Tuesday due to a technical problem just as the Christmas travel season kicked into overdrive and winter weather threatened more potential problems for those planning to fly or drive.

Government regulators cleared American flights to get airborne about one hour after the Federal Aviation Administration ordered a national ground stop.

Meanwhile, the flight-tracking site FlightAware reported that 1,447 flights entering or leaving the U.S., or serving domestic destinations, were delayed Tuesday, with 28 flights canceled.

Aviation analytics company Cirium said Dallas-Fort Worth and Charlotte, North Carolina, saw the greatest number of delays. Chicago, Miami, New York and Washington experienced fewer delays.

Rain and snow was expected in the Pacific Northwest at least into Christmas Day. Showers and thunderstorms were developing in the South. Freezing rain was reported in the Mid-Atlantic region near Baltimore and Washington, and snow was falling in New York.

Because the holiday travel period lasts weeks, airlines typically have smaller peak days than they do during the rush around Thanksgiving, but the grind of one hectic day followed by another takes a toll on flight crews. And any hiccups can snowball into massive disruptions.

That is how Southwest Airlines stranded 2 million travelers in December 2022, and Delta Air Lines suffered a smaller meltdown after a technology outage in July caused by a faulty software update.

Airlines expect to have their busiest days Thursday, Friday and Sunday.