A powerful winter storm that dumped heavy snow and glazed roads with ice across much of Texas and Oklahoma lumbered eastward into the southern U.S. Friday, prompting governors to declare states of emergency and shuttering schools across the region.

Snow began falling in metro Atlanta before dawn, leading to hundreds of flights being cancelled and hundreds more delayed at Atlanta’s airport, according to flight tracking software FlightAware. Controllers declared a ground stop before 8 a.m., meaning no planes could land or take off. Atlanta, a major hub for Delta Air Lines, is the world’s busiest airport.

Four passengers were injured after a Delta Air Lines plane bound for Minneapolis aborted takeoff on Friday morning, according to a statement by officials at the Hartsfield–Jackson Atlanta International Airport.

One passenger was taken to a hospital for treatment, while three people were treated at the scene for minor injuries. The incident contributed to further delays at the airport, although Delta said it was unclear whether the weather had anything to do with the flight aborting its takeoff.

Other airports with significant delays and cancellations included those in Charlotte, North Carolina, Dallas-Fort Worth and Nashville.