WASHINGTON — The U.S. Air Force is nearing a decision on whether to ease weight restrictions on the F-35A caused by issues with its pilot escape system, but if the aircraft's Martin-Baker ejection seat meets requirements, the service will likely abandon plans to qualify a second seat, the Air Force's top uniformed acquisition official told Defense News in an exclusive interview.

The Air Force has prohibited pilots weighing less than 136 pounds from flying the F-35A since 2015, when it was discovered that lightweight operators were at high risk of serious, potentially fatal neck injuries upon ejecting from the aircraft. Martin-Baker — a U.K. firm that manufacturers the F-35's US16E ejection seat — and Rockwell Collins, which makes the helmet, spent more than a year fixing and retesting their products to ensure they meet requirements.

Meanwhile, the Air Force contemplated integrating a different ejection seat. In 2016, Lt. Gen. Arnold Bunch, the military deputy for the Office of the Assistant Secretary of the Air Force for Acquisition, directed the F-35 Joint Program Office to study the potential cost and schedule impacts of qualifying United Technologies' ACES 5.

Martin-Baker and F-35 prime contractor Lockheed Martin have since wrapped up testing and submitted new data to the Air Force, whose airworthiness authorities will make a final determination on whether to lift weight restrictions, Bunch told Defense News on April 17.  

"What I am waiting on to see if the issues that we needed to have addressed have been addressed, and if those have been addressed, I will retract my request for that information [about ACES 5]," he said.

Bunch added that he would wait to see the data before making a final decision and will weigh whether the cost of qualifying a second seat could be justified. But "if the seat that we have meets all of the requirements, I would have a hard time explaining why I would want to spend that money," he said.

Air Force officials have said it could remove weight restrictions as early as this month, followed shortly by a resolution about whether to move forward on ACES 5.

"All the indications that I have right now and the information that I have been given is that all the requirements are being met," Bunch said. "Our No. 1 priority from the very beginning has been the safety of our aircrew. That has been our No. 1 focal point, and the JPO and Lockheed Martin and Martin-Baker have responded and leaned in to address the issue as we wanted them to."

Bunch's comments may signal a shift in perception on the US16E, which had been regarded with apprehension by many in the Air Force since the risk to lightweight pilots was found. Bunch himself signed the memo seeking out more information about ACES 5, and Brig. Gen. Scott Pleus, who heads the Air Force’s F-35 integration office, told Defense News in February that qualifying the ACES 5 seat might be a prudent option to guard against future uncertainty.

Although the service had never committed to procuring the ACES 5 seat, a decision to stick with the US16E would be a major blow to United Technologies, which would be forced to watch a major sales opportunity pass by. The Air Force plans to purchase 1,773 F-35As over the course of the program — a hefty order that would have kept the company’s production line humming.

"Ultimately, the U.S. Air Force is responsible for the safety of its F-35 pilots. While we believe our ACES 5 ejection seat is the safest in the world, we will respect the Air Force’s decision," a United Technologies spokesman said in an emailed statement.

Martin-Baker and Rockwell Collins have integrated and tested three fixes to their products in the hopes of bringing them back in line with Air Force requirements.

A new switch in the US16E modifies the parachute loads to accommodate pilots of different weight ranges, and a head support panel helps guard the head and neck from stress upon ejection. The weight of the Rockwell Collins helmet has also dropped from 5.1 to 4.6 pounds, putting less pressure on the head and neck.

The F-35 Joint Program Office has remained bullish on the Martin-Baker seat throughout the ordeal, with Lt. Gen. Christopher Bogdan, head of the F-35 JPO, repeatedly saying that the modified US16E was making progress in tests and now meeting specifications for pilots of all sizes.

"I have an ejection seat on this airplane now that is better than anything in the field or anything projected to be in the field," Bogdan said in March. "It can handle a pilot from 103 pounds to 240-plus pounds from about 5 feet up to a 6-and-a-half-foot person. That set of body sizes cannot be replicated in any other ejection seat in the world, and it meets the requirement, so as a program manager, I’ve got what I need."

"Yeah, it was painful. Yeah, I had to make some changes to the seat. Yeah, it was controversial. But the seat today meets all of the requirements," he continued. "So from my perspective, I don’t need to look at anything else."