The chaos isn't over for U.S. air travelers.
Delta chief Ed Bastian says the airline faces a couple more days of delays and cancellations.
It's all a result of the global IT outage caused by a faulty software update from cybersecurity firm CrowdStrike.
That sparked worldwide problems for firms that use its software on Microsoft systems.
Delta is among the worst-affected airlines.
It has canceled over 4,000 flights since Friday.
On Monday alone, it dropped over 800 flights,
or around a fifth of the total that day.
That's according to data from plane-tracking app FlightAware.
Travelers in Atlanta, Delta's home base,
were predictably unhappy.
Look around, there's bags everywhere and there's still families just laying on here on the ground since Friday.
People have been here since Friday, so this is ridiculous.
Bastian says Delta is working around the clock to solve the problem.
He said he hoped things would be much better by Wednesday.
Around 60% of critical applications at the firm are Windows-based.
Because CrowdStrike's software operates deep in the Windows system, fixing computers affected by the problem has meant each one had to be manually repaired and rebooted.
Delta has had particular trouble with its crew tracking system, which is meant to ensure pilots and others are in the right place at the right time.