(CNN) — The number of air travelers dropped slightly last week after 12 straight weeks of growth.
The Transportation Security Administration said it screened nearly 4.7 million people last week, down from the 4.8 million the previous week. That's a decline of about 4 percent and is about a quarter of travelers screened on the equivalent days in 2019.
The number of air travelers had been steadily increasing since the second full week of April, when only 670,000 people passed through security checkpoints, according to the TSA numbers.
The agency saw its two busiest days since the pandemic struck during the July 4 weekend.
A nationwide slowdown
Flights are not filling up, with the average domestic flight only about half full.
Major airlines have also said they are seeing a slowdown in business as the number of coronavirus cases climbs nationwide.
The number of people aboard each flight dropped over the last several weeks as total passenger volumes plateaued, the air carrier industry group Airlines for America says.
According to the group, the average domestic flight has about 60 people and is half full.
Delta's CEO called the recovery "choppy" last week, and said "demand growth flattened recently with the rise in COVID-19 cases."
As a result, CEO Ed Bastian said the airline has cut flights from its schedule for August.
The overall drop in travel due to the pandemic has led to some airlines warning employees to expect furloughs when federal aid expires in October.
American Airlines recently warned 25,000 of its employees to expect a possible furlough. United Airlines, which recently reached a buyout deal with pilots, said its cuts could reach 36,000 employees.
The decrease in air travelers is in line with the Automobile Association of America's (AAA) summer predictions, released last month, just before the country's coronavirus cases spiked.
"When they do venture out, the greatest share of travelers -- 683 million -- will take to the road to satisfy their wanderlust," Paula Twidale, AAA's senior vice president of Travel said in last month's news release.