The Air Force said it will slow enlisted promotions for the next two years as it tries to spread Airmen more evenly across the ranks. The service hopes the move will help resolve some of its recent workforce challenges, such as rebuilding institutional knowledge in a young and understaffed maintenance corps. More people than usual are staying in the enlisted force, but the number of jobs is remaining essentially flat. Without Airmen leaving to make room for more junior troops to rise, the workforce stagnates. And without more jobs in the pipeline, the Air Force needs to shrink its cohort of midlevel enlisted so that higher tiers aren’t overwhelmed by demand.