I was asked a question about this in a PM so I have investigated
It is a matter of selecting the appropriate theatre and planeset., and because of the career maps I chose an old map exe
I started with SPAW with the original theatre, and a planeset almost identical to the original although the Avenger replaces the Dauntless
The logbook shows two missions, but before I flew the second one I had started a Luftwaffe career.
Setting up the Luftwaffe career:
After flying the first mission I reloaded the SPAW theatre and planeset.
I was able to load my saved career, and fly the second mission, hence the two entries in the SPAW logbook
Then I returned to my ETO career and flew my second mission:
The logbook shows the results
I was not really trying to fight battles, it was a test of the system and it worked. Because of the way 160 is set-up careers are saved, and easily re-loaded for continuation.
Next I will test the Spanish Air War theatre for careers