DENVER (KDVR) — The Federal Aviation Administration told FOX31 a ground stop at Denver’s airport Sunday morning was caused by lack of air traffic controllers. The delay ended by 9 a.m.

“I’ve had two flights canceled: one on Frontier, one on United,” passenger Rose Hooley said of the Sunday impacts.

More delays may be possible, according to aviation expert Carmen Reale, an adjunct professor of air traffic control at the Metropolitan State University of Denver.

“Because of the controller shortage and the weather, there’s going to be more delays coming up in the summertime,” Reale said.

The FAA said because of the pandemic, the agency shut down its training academy for four months in 2020 and paused training for eight months.

Reale said delays or ground stops are designed to maintain safety standards as the agency works to train and hire more controllers.

“They have to put a delay in so they don’t get overworked,” Reale said.

FAA: Federal spending cuts would wreak havoc

The FAA shared a May 5 letter to Congress on the impact the house budget would have on the ability to hire needed air traffic controllers.

“Given current budget debates in Congress, the report reflects the urgent need for consistent funding for the workforce that maintains the most complex airspace in the world,” the letter reads.

While additional information shows the primary causes for delays in 2022 were weather and problems caused by airlines, rather than controller staffing issues, the letter warns that spending cuts recently passed by the House of Representatives would wreak havoc on summer air travel, forcing the agency to halt training and new hiring and furlough thousands of employees.

“The FAA has told the airlines to reduce their schedules, so because of that there’s going to be a crunch on seats for the airlines to get, and the planes will be full but there’ll be less of them. So it’s more workable for the controllers, because we always have safety as a primary concern,” Reale said.

In order to accommodate the increased demand for air travel in the coming months, the FAA will increase efficiency by optimizing commercial airspace and activating nearly 170 high-altitude routes. This will mean a 13% increase in the number of available seats.

A Denver airport spokesperson said travelers should prepare for delays by signing up for airline alerts, arriving at the airport early and checking security wait times and parking availability on the airport’s website.

Travel experts advise booking the earliest flight of the day to offset the effect of unexpected delays.