During 2017 the U.S. Air Force joined navy by continuing to extend temporary exceptions to the traditional (since the late 1940s) "up or out" policy prevalent throughout the American military. What up or out meant was that if you were not promoted within a certain number of years (of your last promotion), you had to leave. That meant capable, often very capable personnel (especially NCOs and mid-rank officers) with jobs that had little opportunity for promotion were often forced to leave because of this rule. The air force, like the other services, are slowly modifying the “up or out” rule so that it at least becomes tolerable and not counterproductive.
Whenever there were major reductions in military personnel (after World War II, Korea and Vietnam) it was common for a lot of very competent NCOs and officers to be “up or outed” and since last major round of downsizing in the 1990s all the services sought more ways to avoid losing skilled personnel who being lost for no other reason than that there were no opportunities for promotion. After 2001 the navy and air force were hardest hit and both services have implemented temporary adjustments to “up or out” rules to keep people they could not afford to lose and could not easily replace by retraining veteran personnel in other fields or obtain new recruits with the needed skills and experience.
This became a more frequent problem after the Cold War ended and all branches of the military sought solutions. The most common approach, which had been used successfully in the past, was retraining many of these veteran and capable personnel for other jobs where there were shortages. That did not work now because most of the people who had valuable skills, experience and (through no fault of their own) little prospect of promotion were wanted for the skill they already had.
The air force has had a particularly hard time holding onto NCOs with skills and experience in fields like intelligence, UAV operation and analyzing the vast increase in intel data from UAVs and manned aircraft sensors. These jobs often require personnel with high-level security clearances and skills not directly transferable to non-military employment. Moreover these veteran NCO want to stay in, at least until they are eligible for retirement after 20 years’ service. At first the air force solution was to simply extend temporary exemptions to “up or out” rules. The navy has established similar solutions but also has to deal with the problem of having far more people on sea duty, which takes them away from their families for extended periods, than the air force. That has been a problem for the navy, and to a lesser extent the army, since the end of World War II. With the air force, is was mainly about valuable skills and experience.
After 2001 the “up or out” rules became a major problem for the navy and air force because they were actually downsizing (meaning fewer promotions for those remaining) while the army and marines were expanding. Yet even with that the army and marines are paying more attention to avoiding losses of competent people by paying more attention to finding another career field they can train for and get promoted before they are hit with “up or out.” But the army and marines are also noting the success of the temporary exemption policies in the air force and navy would apply to soldiers and marines doing the same jobs. In all services the needed personnel most frequently forced out are relatively young (NCOs in ranks E-4, E-5 and E-6). The personnel benefitting from these policies are veterans with records of good performance, especially when it comes to supervising other troops or performing technical skills that are not easily transferred to civilian careers.
The air force has been faced with this problem for nearly two decades now. Back in 2003 air force leaders were alarmed at the increasing number of veteran airmen who were not reenlisting (often because of “up or out”) and sought ways to hold onto these experienced NCOs during wartime. They found that one minor change that worked wonders was to allow NCOs to remain un-promoted longer before being forced to leave the service.
But by 2008 those shortages were gone and there another downsizing effort meant to reduce strength to 318,000 (a loss of nearly 40,000 personnel). Then a change of air force leadership in 2009 reversed that downsizing plan. The earlier downsizing was partly the result of the 2008 recession, which has led to a lot more, high quality, people trying to get in. The air force took all it could get, and then decided to cut some of the less qualified people it already had. Thus the decision to make it more difficult to get promoted and many NCOs with valuable skills were being forced out.
The air force has long been accused (by members of the other services) of operating more like a corporation than a military organization. That's a little harsh, because the air force is the most tech minded of the services, and has always taken the lead in adapting commercial innovations to military use. But sometimes this thinking collides with the fact that the air force is a combat outfit. Especially during the Iraq and Afghanistan operation, more air force personnel found themselves under fire. Not pilots, but over 20,000 non-pilots that volunteered to help the army by doing support jobs in the combat zone. The air force was persuaded to create a Combat Action Medal for airmen who saw battle action on the ground while serving with the army. In two years, over 2,000 of these have been awarded. But in addition volunteering for that combat zone work and doing well helped your promotion prospects, especially as more and more air force squadrons were sent overseas. The air force sent units over for shorter (three months) more frequent tours. Thus air force NCOs with combat zone experience, became much sought after, no matter what their primary job was. But even that was only a temporary solution to the “up or out” problem and the air force is joining the other services to modify “up or out” as much as it takes.