Yet another aircraft bug

Here's yet another one. I have been attacking a stack of enemy ships with two stacks of tac bombers and interceptors, flying from the same base. Each stack has 2 interceptors and 5 bombers and I've been spacing the raids about 5 minutes apart. This seems to work fine most of the time, however if I leave the game and return, I find they have combined into one big stack of 4 interceptors and 10 bombers. Not only does this reduce their combat effectiveness by about 50%, but combat results indicate to me that "oversized" aircraft stacks take heavier losses.