[Nicholaiovitch]

I've only just noticed that flying a P39D-1 USAAF using the New Guinea QMBPlus map with the target set to Airbase all except one of the Japanese aircraft on the ground have German markings.

How can I change this please?

You need to modify the "Template" mission for this map and scenario (Airbase)...
1) Look at the list of files in your root folder of IL2
2) In the root folder you should see a folder called "Missions". In that folder...do you have a file called "Quick"? If the answer is "yes"....go to item 4) below
3) If there is no "Quick" file in the main "Missions" folder.......find the "Mods" folder in the root directory and look for the QMBPlus file. In there you should find a "Quick" file. Copy this file and paste it into the "Mission" folder in the root directory.
4) Open the FMB and load the mission named "NewGuineaRedAirbase00.mis" from the "Quick" folder in "Missions".
5) Click on each of the ground based a/c and change them to the nationality you require.
6) Save the mission (same name)
7) Depending on the method you installed your Mods (UI or "one at a time" with the sound mod")
you may need to copy this new mission to the "Quick" folder back in the QMBPlus version of your "Quick" folder (In Mods) You can however try running the mission without this step, and if it works, in future you can dispense with the "Quick" folder in the QMBPlus.

I'm sorry this is so longwinded. Take it a step at a time and you will be OK. Once you have the hang of it, you will be able to mofify any of your QMBPlus missions i.e bring the combat nearer, change location on the map etc.

Good luck.

Nicholaiovitch