Two other scenarios that aren't as suspicious...

1. Buying/leasing enough aircraft to the end of the game. In SC-3, the MD-11 goes off-market in 2000, but I leased 300+ to last me through 2024. The last few games years, the aircraft are simply swapped out as they arrive to lower the average fleet age to help increase reputation.

2. Deferring aircraft delivery multiple years. Same concept as above. In SC-3, I had picked up 25 MD-90-ER's on the used market, so I bought 25 more and deferred them all the way to the final game year to do a swap to lower average fleet age. I do this with any aircraft whose end-of-life is before the last game year.