There is something very wrong with the used market though.
One or two big airlines buy planes just to get that achievement. The used market is loaded with planes that need C and D checks.
I'm not entirely sure what the restrictions to buying new aircraft are but I think there should be some, or that achievement has to be taken out because this is truly idiotic. Check the used DC8's and Boeing 707's and 747's for fun. They are bought for no other reason than to end up on the used market and to rot there. That's ruins the balance of the used market completely and indirectly also spoils the new airplanes market.
I mean honestly, who needs 40 Concorde's other than for the achievement?
The flip side of course is some of those planes have been lowered in price as much as the system allows. If you're willing to C or D check the plane you can still get them for a bargain.
If Sami scrolls through this, a possible long game feature improvement might be to lower the scrap age on pre-1965 (or similar early 1960s date?) planes. I notice if you turn in a leased Hawker 121 right before the 8 year D check, the system is scrapping many of them (otherwise the high number of H121 scraps doesn't make sense as they are well below 16 years). Of course if I put an owned one into the used market, I have to wait another 8 years to scrap them.
Maybe in the next JA certain planes like Caravelles, Any turbo props (DC, Lockheed) and the early jets comet1-3' DC-8 10-43s could have a 10 year scrap as that might help clean up the 3 pages of DC-8-10 through 30s that are now parked. Granted some folks will keep them parked for the MV boost, but I'm a fan of use them; offer them; then scrap them and move on.
Also I don't think this is too far fetched for the 1960s with the massive improvements in technology in that decade.