Winter storms are still plaguing Delta Air Lines flights as holiday travelers try to get to their destinations.

Atlanta-based Delta waived change fees for customers with flights booked in the Northeast, Midwest and South central regions of the country earlier this week due to winter weather.

It's a move aimed at allowing those whose schedules allow it to attempt to avoid flight delays or cancellations. Those travelers have until Thursday or Friday to rebook flights.

Nov. 20, 2015 - Atlanta - Kellan Trawny, 5, from Smyrna, keeps watch on the family dog while his mom checks in at the Delta Kiosk. Record crowds are expected along with long lines and delays at Hartsfield-Jackson Atlanta International Airport, the world's busiest airport, which is forecasting some of the biggest increases in traffic it has seen in years. BOB ANDRES / BANDRES@AJC.COM

Credit: Kelly Yamanouchi

icon to expand image

Credit: Kelly Yamanouchi

That comes after big challenges on Christmas. On Monday, Delta CEO Richard Anderson said in a message to employees: "We had pretty tough weather across the system, particularly in Atlanta around Christmas, on Christmas Day." He said many crews ended up laid over due to tornadoes across the South and four inches of rain in Atlanta.

Anderson said through last Sunday, Delta was scheduled to operate more than 17,000 flights, many more than 90 percent full.

On Twitter, some customers complained to Delta about problems with flight delays, cancellations, baggage and struggles to get rebooked.

"I know it can be frustrating with flights cancelled due to weather," one Delta agent tweeted to a customer.