Very simple question.
 

From a little experimentation, it seems airbases don't actually spawn aircraft. My question to anyone with more experience than me, do they? And if so how can I get them to on my various missions I create. Simple as that! If they don't, any ideas on how I can get aircraft to arrive after U-BOATS attack. Reinforcements pretty much.

Hi ZipperZuperZinga Welcome to Subsim
re spawning aircraft will spawn in single player missions and multiplayer missions due to the LND LAND Leyer in the data campaigns campaign folder.
when you open up the mission editor then open the LND file you see the airbases and the yellow radius circles around the airbases and as the war progresses those radius circles increase in diameter as new aircraft become available with longer range and more in number.
When you write a early war mission may 1941 outside the aircraft spawn radius then no aircraft will spawn.
In the multiplayer missions I have written 30-60mins in to a 2 hour mission land based aircraft spawn also if you have a escort carrier within the convoy escort screen carrier aircraft spawn also.
In your sh3 folder go to documentation folder open up SH3 MAP shows you aircover coverage in the Atlantic by year

hope this helps you regards blackswan40