Polly and I fly on Air Mobility Command (AMC) Space Available flights once or twice a year. The Space A program allows those eligible to use otherwise wasted seats on military and military-contracted commercial aircraft. Travel on military aircraft is free. Travel on military-contracted commercial aircraft is very economical, e.g., $70-and-change for Polly and me to travel in April 2015 from Aviano AB, Italy to Baltimore-Washington International Airport with a three hour layover in Ramstein AB, Germany aboard a Boeing 767.
Space A flights are not guaranteed, but then neither are commercial if you think about it. We flew out to Germany on that April 2015 trip on commercial air from Indianapolis, Indiana. We were delayed three hours in Indianapolis because a bird impact had scratched the nose of our airplane, would have missed our connecting flight, appealed to the Delta agents, and caught a direct flight from Indy to JFK where we had less time than planned to board our Norwegian Airlines flight to Munich. Our only similar negative Space A experience was mine in – stupid me – early July 2014. I was trying to save money by coming home from the United Kingdom during the summer rush season for higher priority category Space A travelers. After three days missing Mildenhall AB flights back to the United States because of my low Category 6 status, I bit the bullet and bought a commercial ticket out of Heathrow, near London. Polly and Aaron had sensibly bought round trip commercial tickets.
The six priority categories logically start with Category 1 active duty military members on orders and end with my retired military “Cat 6”. By considering the times of year for our Space A travel, signing up online in advance, and contacting the Space A “PAX” (passenger) terminals involved close to expected flight dates to verify the situation we never before or after had any more such Mildenhall experiences in spite of our Category 6 status. As in all things, use common sense.
The following linked article has much more detail and suggestions.