A key step toward possibly opening the Air Force's last male-only combat jobs to women concluded June 19.

That day, the Air Force's Air Education and Training Command finished testing 175 male and female volunteers over two months at Joint Base San Antonio-Lackland on the kind of physical challenges they would face on the battlefield, said Neal Baumgartner, exercise physiology and fitness consultant to the Air Force and AETC's program director for fitness.

And the service will use the results to set the first gender-neutral occupational standards for those jobs, linked to specific tasks battlefield airmen will be expected to do in combat.

"Ultimately, the initiative to eliminate any remaining gender-based assignment restrictions will improve our readiness and the Air Force's ability to recruit and retain the most effective and qualified force," Air Force Secretary Deborah Lee James said in an April release announcing the tests.

Brig. Gen. Brian Kelly, director of military force management policy, said in April that the tests will help the Air Force set tests that will show which airmen can succeed in the physically demanding combat jobs.

"This effort marks the most stringent process yet by which we are developing occupationally specific physical standards, scientifically measured against operational requirements to match mission needs," Kelly said.

The Air Force's combat jobs that remain off-limits to women are 13C special tactics officers, 13D combat rescue officers, 15WXC special operations weather officers, 1W0X2 special operations weather enlisted, 1C2 combat control, 1C4 Tactical Air Control Party and 1T2 pararescue. Combined, those seven career fields represent roughly 4,300 special operations positions.

Battlefield airmen have to do a wide variety of physically demanding tasks in their line of work — drag a wounded comrade on a sled or hoist him on a litter, launch a boat, rescue people at sea, climb rope ladders, climb over walls, ruck over long distances into enemy territory, among many others. But setting up real-life scenarios to test each of those abilities would be too complicated and expensive to do on a regular basis. So the Air Force is trying to match each of those tasks with regular physical fitness tests, such as pullups, distance runs, lunges, standing long jumps, and dead lifts.

The Air Force had actual special operators such as combat controllers score the simulated tasks for how frequently they encountered them, how intense they are, how long they were expected to do such tasks, and how critical those tasks were to accomplish their mission. For example, if someone can't carry supplies to an aircraft, Baumgartner said, that's a problem, but it might not scuttle the whole mission. But if someone can't climb a rope ladder into a helicopter, that could cause the mission to fail.

"A lot of effort and analysis went into developing those [simulations]," Baumgartner said.

Then, once the critical task list of the most arduous, important tasks was set, volunteers each spent 10 days at Lackland. The first week, they did 39 fitness tests to assess their agility, power, muscular strength, muscular endurance, and anaerobic and aerobic capacities. The second week, they performed 15 different task simulations mirroring what they would encounter on the battlefield — swimming, wall climbing, and dragging dummies to simulate casualties. For example, Lackland built a structure to the exact specifications for a C-17 ramp, and had airmen carry a simulated litter to the top of the ramp, raise it, hold it, and then mount it in the simulated aircraft.

The Air Force will next correlate and analyze the results of both the physical fitness tests and the battlefield simulations to see where they line up. For example, if some airmen do well on pushups and also do well on the litter carry, and other airmen don't do well on either, that could be a sign that they go together. And instead of having to stage a litter carry on a C-17 simulator to figure out if someone can hack it, the Air Force could give them a pushup test and other tests that correlate with litter carrying abilities.

The Air Force says the testing effort will not mean lower standards to accommodate women.

"The key is to ensure we have set the right standards for the occupation based on mission requirements," Kelly said in April. "The effort is built upon science and experience, to ensure we continue to maintain our readiness and preserve the quality and capability of our all-volunteer force."

Baumgartner said AETC is trying to figure out which tests can predict success on the battlefield, regardless of whether the airman is a man or a woman.

"Whether it's a male or female is not the issue," Baumgartner said. "It's 'Can the operator maintain status and can we select people that have the physical raw abilities that they can then train up to that status?'"

Baumgartner said his team at AETC has until July 31 to provide its recommendations on standards to Air Force leadership. After that, the Air Force and other services will make their own recommendations to Defense Secretary Ash Carter in August or September, he said.

Carter is expected to send his own recommendations on which jobs should be opened up on or about Jan. 1, when Congress will then choose to act on or not.

In a March speech outlining her plans to increase diversity in the Air Force, James reiterated her desire to open up these combat jobs to women.

"And boy, the burden of proof will be heavy on any recommendation to keep any of these positions closed once we have gender-neutral, job-relevant standards in place," James said.