Hi Freddio and welcome to SAS
Our good old Ultrapack dates back to the times when IL-2 didn't support widescreen resolutions per default, but it's quite easy to get there.
To get the game to run in your native solution, please open the file "conf.ini" from your UP3 game folder and adjust the following values from the "[window]" section which should be more or less at the beginning of that file:
width=1920
height=1080
FullScreen=1
ChangeScreenRes=1
ColourBits=32
DepthBits=24
StencilBits=8
DrawIfNotFocused=1
EnableResize=0
EnableClose=1
SaveAspect=0
Use3Renders=0
You cannot choose these values from the ingame menu, that's why you have to do it manually in conf.ini.
This will let your game start in your monitor's native resolution, however all menues will still show up in 4:3 format.
To fix this, please download and install the "Ecran Wide" mod for IL-2 4.10.1:
https://www.mediafire.com/file/16uscdzm1z41axy/Ecran_Wide_4101.7zNote that even if UP3 offers "WideScreenSupport" and other nice sounding features in JSGME,
you must not enable these as they're outdated and will ruin your game.
Don't use "#UP#_Enable_Hakenkreuz", "#UP#_Enable_WideScreenSupport" or "#UP#_Enable_Hakenkreuz&WideScreenSupport", only choose "#UP#_Enable_UP3.0" and use Ecran Wide mod for Widescreen Support, Hakenkreuz enabler is included in the Patch Pack.
Best regards - Mike