Heavy travel day off to a rough start after American Airlines briefly grounds all flights

American Airlines briefly grounded flights nationwide 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 Tuesday about one hour after the Federal Aviation Administration ordered a national ground stop, which prevented planes from taking off. Meanwhile, the flight-tracking site FlightAware reported that 1,447 flights entering or leaving the U.S., or serving domestic destinations, were delayed. Twenty-eight flights were canceled. Millions of travelers are expected to fly over the next 10 days. The Transportation Security Administration expects to screen 40 million passengers through Jan. 2.