The U.S. Air Force is struggling to fill a shortage of 700 fighter pilots by the end of the year, even as the U.S. battles in three air wars against ISIS in Iraq, Syria and Libya.

“It is a crisis,” said the U.S. Air Force’s new top officer, Gen. David Goldfein, aside Air Force Secretary Deborah Lee James at the annual “State of the Air Force” briefing at the Pentagon Wednesday.  

“Air superiority is not an American birthright," Goldfein said. "It’s actually something you have to fight for and maintain.”

Fox News first reported the Air Force shortage of 700 pilots after visiting two Air Force bases in May. 

Airmen told Fox News, in addition to the pilot shortage, they are 4,000 mechanics short as well. 

Shorthanded crews are now forced to scrounge for spare parts in museums and the “boneyard,” a graveyard of planes in the Arizona desert to fix their planes because the parts are not made anymore. 

Air Force Secretary Deborah Lee James said Wednesday that she is planning to pay drone pilots a $35,000 a year retention bonus to encourage them to stay in the service.

The $35,000 a year retention bonus would be an increase over $25,000 bonus the service has been allowed to provide, and all drone pilots would be eligible once their service contract is up.

James added that Air Force needs the authority to increase bonuses for all pilots in order to address the shortage.

The Air Force has grappled with pilot retention for some time, particularly as airlines look to hire them, promising higher salaries and benefits.

James said the pilot shortage could grow to 1,000 in a couple years. An Air Force spokesman told Fox News that may be by 2022.

"The airlines are forecast to be hiring a lot more," she said, adding that the Air Force also needs to increase its training of new pilots.

James and Goldfein said they want to improve pilots' quality of life and their military service conditions, including training and housing.

Goldfein said fighter pilots are leaving at a higher rate, and that improving their quality of service as well as beefing up the retention bonus will help address the problem.

Fueling that problem, he said, has been the persistent overseas deployments as the U.S. has been engaged in air wars for more than two decades.

"If we take a balanced approach, we're hoping that we can get these folks to stay," he said.

Goldfein said that so far the pilot shortage isn't affecting air operations over Iraq, Syria and Libya, nut the ongoing deployments continue to affect pilots' decisions on whether to stay in the service.

The Air Force's current fleet of planes is the oldest in history.

Fox News’ Lucas Tomlinson and the Associated Press contributed to this report.