A day after the airline canceled 1,000 flights, Delta said it canceled another 250 flights from Tuesday's schedule. And about 200 morning departures are expected to be delayed.

"We are still operating in recovery mode," said Dave Holtz, a senior vice president at the world's second-largest airline.

The outage Monday grounded Delta (DAL) flights for at least six hours, stranding hundreds of thousands of passengers around the globe.

The airline is scrambling to redeploy crews and aircraft as the impact of the outage rippled through the system. Experts said it will be Wednesday, at best, before the schedule can be back to normal.

The airline is offering refunds to passengers on canceled or "significantly delayed" flights. It also said passengers whose flights are canceled or delayed more than three hours will get $200 travel vouchers for future flights. Delta will also waive change fees for any passenger originally booked for Monday or Tuesday.

Aviation experts said the outage and subsequent problems will likely cost Delta tens of millions of dollars.

Delta said the problem was set off by a power outage at its Atlanta hub and the failure of key systems to switch over to backup power.

The company said it's continuing to investigate what exactly went wrong.