Article: Specific concerns include a compounded inability for the Air Force to replace its aging fleet, and an overall reduction of strength and readiness. The USAF attempted to make these adjustments by primarily cutting the Air National Guard and Air Force Reserve aircraft fleets and their associated manpower, but Congress reversed this initiative and the majority of the lost manpower will come from the active forces. However, Congress did allow for $208 million of reprogramming from fleet modernization to enable some portion of the third of the grounded fleet to resume operations.

Question: What is one of the concerns of the Air Force?
replace its aging fleet