An estimated 77,500 people are expected to stream through security checkpoints at Hartsfield-Jackson International Airport on Wednesday, the second-busiest day of the Thanksgiving travel period at the world’s busiest airport.

Lines were already backing up to the domestic terminal atrium early Wednesday morning.

Airport and Transportation Security Administration officials advise travelers to get to the airport 2.5 hours before their flight. Security lines have been more than half an hour long during peak periods in recent weeks.

The busiest day of the Thanksgiving travel period at the Atlanta airport is expected to be Sunday, when more than 88,000 travelers are expected to be processed at TSA checkpoints.