Quick refresh me...requirements for upgrading air units?

[TommyBoy84]

Hey all,

Quick question that I can't find an answer to by search, and I've learned not to trust the manual....

What are the requirements to upgrade an air unit to a different type of plane? I attempted it at a large base (don't want to give my PBEM partner(s) and hints as to where), but was told something to the effect of the base either didn't have enough supplies or wasn't close enough to a/the HQ unit.

So, in short, what are the requirements to be able to upgrade an air unit again?

Thank you!

[Yamato hugger]

20,000 supply and enough planes in the pool.

[Anthropoid]

ORIGINAL: Yamato hugger

20,000 supply and enough planes in the pool.

Doesn't it have to be in range of an Air HQ of the same HQ?

Another thing is that, there are certain 'even't coded limitations. For example, Brits (in stock) cannot upgrade airplanes until May 1942. Maybe others too?

[Yamato hugger]

ORIGINAL: Anthropoid

ORIGINAL: Yamato hugger

20,000 supply and enough planes in the pool.

Doesn't it have to be in range of an Air HQ of the same HQ?

Another thing is that, there are certain 'even't coded limitations. For example, Brits (in stock) cannot upgrade airplanes until May 1942. Maybe others too?

Only has to be in range of a HQ if there isnt 20,000 supply at its base, then there has to be 20,000 at the HQs base.