Why not make the game round based, for example the server lasts from 1990 to 2020 (and speed like one actual day is a months) and the winners and high finishers get medals. We could have a new server starting every months or so. Airplane models need fixing with correct data(they are not realistic right now)
You definitely need to monetise the game for a better server and ice-cream. As an example sell in game currency for 1usd = 1 million in game or something(so its not too overpowered and attractive to use), maybe some advert banners.