If I understand correctly, you need to replace one of your lower level planes with the jet. Sell the lower level plane while it is landed and buy a jet. This way you'll be able to fly to Singapore. Other option is to ask for required item for tower upgrade from your neighbours.hi all! I'm trying to upgrade my control tower to level 4 but I need to fly to Singapore to collect stuff for upgrading it. But I can't buy jet to flight without control tower... How can I do?
Thanks all!