Airfield / groups number limited?

[LLv34_Temuri]

Is there a limit to how many airfields there can be in a mission? I was making a mission where an airfield is inside a group with the rest of the airfield objects. I added 11 such groups to the mission and everything was ok. After adding the 12th group, the group didn't show up in the objects list shown on the left side of the mission editor. However, when I inspected the mission map, I noticed that the group had been added to the mission.