Diverted flights

At least 827 flights had been diverted due to the ground stop. As of 7:05 p.m. EST, 670 flights were sent back to the airport from where they originally took off, while 157 were redirected to a different airport, according to Cirium, an aviation analytics company.

The airports where many of the flights ended up being diverted included Washington Dulles International Airport, Los Angeles International Airport, Cincinnati/Northern Kentucky International Airport and Nashville International Airport.

Some 11,000 flights carrying more than 1.5 million passengers had been scheduled to take off from airports in the U.S. after 4 p.m. EST.

At the time of the ground stoppage, 3,500 airplanes were in the sky, officials said.