McDonnel Douglas was bought by boeing in the mid to late 90's I believe. The only surviving aircraft that boeing manufactured was the MD-95 which goes by the designation Boeing 717. That model was discontinued in mid 2000s, not sure the exact date. So in the game now you will only find used MD's in the game. The boeing 717 is an expensive plane to run so I don't recommend using it you are better off going with a newer airbus or boeing plane at this point if you want a younger fleet.