Spoils of war - bug?

[nikivdd]

On turn 7 i want to capture the airfield on hex (17,17) which is currently occupied by a Russian bomber. There are 3 of my units nearby able to do the job but the game doesn't allow me to capture the hex. Only after i took care of the enemy bomber, than i can put my flag there. Could it be because it was a white flag before or is it smth else? I kept a savegame just incase someone would want to check.

[Kerensky]

Sounds strange, but what unit did you try to capture the airfield with? Artillery and air defense units cannot capture flags.

[nikivdd]

The 3 units in range from the airfield (17,17) , was a pioniere, a towed AT gun and a recon unit

I put the savegame here:
http://www.sendspace.com/file/gyisbe