AUSTIN (KXAN) – Delays and cancellations happened most of the day Thursday at the Austin-Bergstrom International Airport (AUS), the airport said.

The delays weren’t because of inclement weather or staffing shortages but rather because of cleaning.

“The FAA Air Traffic Control Tower is undergoing a required sanitization & deep clean. AUS will be experiencing delays for both arrivals and departures. Thank you for your patience,” the tweet said.

In a follow-up tweet, AUS said “anyone picking up a passenger from the terminal should monitor their flight status and contact their airlines for updated information.”

“The FAA temporarily closed the control tower at Austin-Bergstrom International Airport today for COVID cleaning. Per standard FAA protocols, the local approach control assumed the tower’s airspace,” the agency said in a statement.

Approach control posts monitor flight paths on radar systems once planes start to descend, and hand off to airports’ Air Traffic Control Centers once planes get within three to five miles of the airport, according to the FAA. Air Traffic Control monitors plans from that point until landing. The FAA spokesperson said approach control operations can handle taking over the workload — this process just slows the flow of traffic, which is prompting delays.

The FAA said tower closures like this are not unusual, and cleaning typically takes one to two hours depending on the availability of cleaning crews.

An employee who KXAN verified works at the Air Traffic Control Tower at AUS said it took about five hours for a cleaning crew to arrive Thursday. He asked to remain anonymous to protect his position at work.

“It seems like it should have been much shorter,” he said. “Definitely a headache — a ripple effect that could take the next 24-48 hours.”

He also said he wishes the process for COVID-protocol cleaning was more streamlined and efficient.

The delays could stretch until midnight Thursday until Friday, according to FAA. The agency encourages Friday travelers to keep a close eye on their flights, given the widespread delays across the country for a variety of reasons.

On the FAA website, the average delay time was listed as 188 minutes, with the maximum delay time listed as 289 minutes.

There were multiple flight delays and cancelations for the Austin airport listed online Thursday afternoon.