All American Airlines flights nationwide were halted Tuesday morning. Why it matters: The nationwide outage threatens to snarl traffic on Christmas Eve for the world's largest carrier. Catch up quick: Bloomberg reported the airline may be experiencing a software issue.

A nationwide ground stop has been lifted after American Airlines grounded its flights for around an hour across the US on Christmas Eve amid one of the busiest travel periods of the year.

American Airlines has grounded all flights on Christmas Eve morning, throwing travel plans for millions into disarray. What you need to know.