Read this: Due to the Budget sequestration in 2013, the USAF was forced to ground many of its squadrons. The Commander of Air Combat Command, General Mike Hostage indicated that the USAF must reduce its F-15 and F-16 fleets and eliminate platforms like the A-10 in order to focus on a fifth-generation jet fighter future. In response to squadron groundings and flight time reductions, many Air Force pilots have opted to resign from active duty and enter the Air Force Reserve and Air National Guard while pursuing careers in the commercial airlines where they can find flight hours on more modern aircraft.

Why have many US Air Force pilots opted to resign from active service? 
What is the answer? (If it cannot be answered, return "unanswerable")
squadron groundings and flight time reductions