I'm playing in S2 and decided to sell all my aircraft (ATRs) in order to use the value to by Q400s for their better range and speed. Because there would be a gap in the time I sold my ATRs until my Q400s arrived when I would temporarily have no aircraft, I returned all gates at all airports.
Now that I am getting Q400s and leasing (fewer) gates again, I find that instead of having "0" gates at AUH from which to lease 1, I have "-6" gates, after leasing 1 going to -5, and the monthly gate cost in my Gate Leasing tab of the finance window is currently a negative number.
Something tells me this is not intended, I believe this is a glitch.