If airports were such a poor financial prospect you wouldn't have significant numbers of them falling into the hands of various financial organisations very much at the speculation end of the scale.
Profitability may be one goal, but another is the increase in asset value over the short/medium term (these sorts of businesses don't do long term).
London City, pretty small in the scale of things, now seems to be regularly sold on from one financial organisation to the next, each time at a notable increase (maybe double) what was paid for it some years before.