More than 3,000 planes are parked nationwide.

The number of air travelers is down more than 90% in the U.S. due to the COVID-19 pandemic, according to the TSA — but U.S. airlines are gearing up.

Carriers’ maintenance teams are spending countless hours to ensure their planes are ready to take to the skies when demand picks back up again.

U.S. airlines have been forced park to more than 3,000 planes nationwide, according to Airlines for America (A4A), an industry trade organization that represents major U.S. airlines.

United Airlines has placed 70 aircraft into storage alone at Dulles International Airport, one of the airline’s hubs.

“It’s not like parking your car,” Travis Allee, a Tech Ops Supervisor for the carrier, told ABC News.

While on the ground, each aircraft undergoes extensive checks to maintain its systems. This includes covering up the engines to keep wildlife from nesting inside aircraft, and running the air conditioning system to evacuate humidity and moisture from the cabin.

Fuel is even kept in the planes to maintain ballast in the event of a wind storm.

These checks can occur every seven, 14, or 30 days depending on the aircraft type.

“An aircraft has a lot more components to it than your standard automobile does,” Allee said. “You don’t have flight controls or a hydraulic system on your car.”

Allee says this work is critical because “there is no side of the road to pull over to at 30,000 feet.”

The airlines have taken an unprecedented financial hit due to COVID-19, and United CEO Oscar Munoz said in an internal letter to employees that even when travel demand starts to “inch back,” it “likely will not bounce back quickly.”

But when that demand does increase, Allee believes the tasks him and his team perform every week will ensure that the transition back to the tarmac is “quick and smooth.”

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