As it always seems that the airfield having the most money spent on it is normally the one most likely to close
As others have pointed out, spending lots of dosh is not an indication of retention. cf Acklington, Stradishall, Finn, Chiv etc, etc.
(Thank you Gainesy)
the answer must be to think laterally and look for the airfield that has had the least spent on it as the one most likely to stay open.
May I therefore suggest Chetwynd as the most likely candidate (although the man that cuts the grass is an ongoing expense). I look forward to seeing all ISK assets operating out of there!
PS Just watch out for the soft bit at the South Western end - it still hasn't recovered from the attentions of the Herc that tried to plough it up