The upkeep for aircraft stacks behaves very weird in my current game.

As seen in the following two screenshots from my current game these stacks of four have an upkeep of 8 each, which already is way too low.

I do not know what modifiers lead to this problem, since hovering over the upkeep does not display a breakdown.

After putting three of the units from one stack into another this happens:

Now the stack is actually generating money, and a lot at that. Also the money from territories in my sphere of influence increased for some reason.

If i now put all eight units into one stack this happens:

The stack now has an upkeep of over 70k, additonally my money from territories in my sphere of influence goes to negative 33k.

This problem persists over turns, splitting the stacks again resolves the problem.

Saves:

Save at the state of the first two screenshots: Aircraft Stack Bug Pre.ctr

Save at the state of screenshot 4: Aircraft stack bug post.ctr

Diagnostics files: Diagnostics.rar

Log file: Player.log

Steps to reproduce:
1. Selecting one of the aircraft stacks.

2. Merging any number of them with the other stack, outcome depends on number of merged units as seen in screenshots. 

I can confirm this bug. 

A full stack of airplanes (4 strategic bombers, 4 monoplanes) send my economy from +20k to -75k.

I deleted 1 monoplane => economy is back to normal.

(Thanks to SomeCheekyBloke, I would never have guessed this is the reason.)