So, I dunno, was thinking more than is possibly healthy. Here's the thought....
When you capture a base, it degenerates into a single mud airstrip as, territory captured in war isn't usually in great condition after a battle. The longer you hold the base for, the more it generates (the longer you hold the area, the more amenities are available to you), say;
0+ hours - mud strip
4+ hours - small airfield
7+ hours - medium airfield
9+ hours - large airfield
If the field is re-captured it degenerates and the cycle is started again.