The Air Force's top non-commissioned officer on Wednesday sought to assure an enlisted force worried about the service's plans to cuts its end strength and introduce a new performance evaluation and promotions system.

"If you look at all the uncertainty that's out there, it's been a challenging year," Chief Master Sgt. of the Air Force James Cody told airmen at the 2014 Air & Space Conference on Wednesday. "The hardest thing we've had to do is ask great airmen to leave [because of downsizing]."

The Air Force in 2014 is the smallest in terms of personnel , he said, even though the force has also been involved in the longest period of American combat operations in history. As of June there were just fewer than 260,000 enlisted personnel in an Air Force of about 325,000.

The Air Force is scheduled to lower its total active-duty end strength to 311,000 next year and with even more cuts – about 19,000 airmen – by 2020.

Already more than 3,500 enlisted members through the rank of senior master sergeant were let go under a Quality Force Review Board and another 1,400 personnel were dismissed under enlisted personnel boards.

In addition to a personnel drawdown, the Air Force is also going ahead with major changes to how it evaluates and promotes its enlisted force.

The changes include a selection board process added to the senior NCO promotion system and the eventual elimination of points for time-in-grade and time-in-service. It is also changing Enlisted Performance Reports to cut down on grade inflation with so many airmen earning top ratings of "5" in all categories -- often referred to as a "Firewall 5."

The inflated scores eventually made the system meaningless as a way to measure performance. Cody said the flaw in the system was "us" – that is, supervisors who routinely handed out "5s" as a way to advance or look out for their own people.

"We have to evolve the systems that have been in place a long time, that have worked for quite some time ... and need to think about what they need to do in the future," he said.

The downsizing and personnel changes are significant and challenging, he said, but necessary.

"This enterprise is bigger than any one person and ... it has to go forward," Cody told the gathering. "But we're going to be okay. We're going to be better than okay."

-- Bryant Jordan can be reached at bryant.jordan@monster.com