US Air Force has ended a restriction that prohibited pilots of a variant of the F-35 fighter jet from weighing less than 136 pounds.
The restrictions were imposed after testing showed lightweight could injure pilots or even can be fatal while ejecting from the aircraft.
"The Air Force is lifting the lightweight pilot restriction from our entire F-35A fleet," Brig. Gen. Scott Pleus, the Air Force's F-35 Integration Office director, said in a statement Monday.
The policy change was made possible due to modifications to the pilot's helmet and the aircraft's ejection seat, Air Force officials said.
The helmet was made lighter while the opening speed of the parachute was delayed, and a head support panel was also added to prevent the pilot's head from moving backward during the ejection.
"Combined, these changes reduce the risk to lightweight pilots in both high- and low-speed ejections, and makes the F-35 ejection system one of the safest in our entire inventory," Pleus said.
The changes to the seat and production of the new helmet will take place over the course of the next few months, allowing for lightweight pilots to begin flying the F-35A by the start of 2018, Pleus added.
The weight restriction was imposed in 2015 after concerns were raised by the Pentagon's testing office about the risk of neck injuries during ejections.
The Pentagon's report found that lightweight pilots had a 23% chance of being killed and 100% chance of being injured by the ejection process.
The Joint Strike Fighter, which has been labeled the most expensive military weapons program in history, has been beset by problems during its development but has begun to be operationally deployed abroad.
Its proponents have noted that the price per aircraft has begun to come down, with the Air Force's version falling below $100 million.
The Air Force plans to buy 1,763 of the stealth jets. The US Navy, which operates its own not yet operational variant of the jet -- the F-35C, has not yet announced plans to modify the ejection seat or helmet, but Navy jets like the F/A-18 already have weight restrictions in place.
The US Marine Corps operates its own version of the jet, the F-35B. The Marines will retain the weight restrictions for the time being but the service is fielding a new helmet this summer that may allow lightweight pilots to clear the restrictions in place.