- only buy airlift capable aircraft if there is one friendly cp without a factory which can only be reached via airlift
- prevent that an airlift procurement gets fulfilled at a different cp than the requesting one. this ensures that the cp also has a factory to produce ground units which can then be transported
- fixes an infinite buy loop if the fulfilling cp has no factory and the requesting cp has no space for airlift
- have always 2 reserve transport planes at the biggest CP