The alternating white and black pattern was designed when the allied command readying up for operation overlord concluded that the thousands of aircraft to be involved during the invasion would make difficult friendly identification and so only visual could be used to identify allied aircraft, the marking scheme would be approved on May 17, 1944 and on June 1 a small scale flight would be made over the OVERLORD invasion fleet to teach the ship’s crews to recognize the markings.
However the order to paint the stripes on bombers and fighters units where not given until June 4 to avoid raising eyebrows on the other side of the English Channel.
This decal will have a rectangular shape to make easy the wrapping around wings fuselages and would be found on the folder Allies>Aircraft. Note that some planes already have the stripes integrated into their paint schemes in game.
Photos of aircraft with the stripes applied onto them
GIB me my invasion stripes (they should have this decal mirror on wings in all directions automatically though
Also, small correction, there were no IFF systems in use during Overlord or most of WWII, and the invasion stripes were used as identification markings.
Dunno about overlord/ETO, but in the pacific theatre there were IFF systems including airborne variants! They were pretty bulky, and originally it was 1 lead aircraft equipped with such that led to a fair bit of misidentification - but it existed!
Way it worked was through a receiver that recognized specific incoming frequencies and responded to the RADAR signal in such a way that it effectively doubled the signal.
Edit: I recall there being issues as well with secrecy. The IFF transponder must not be recovered by the enemy, so pilots were instructed to fry the system before bailing or ditching. The initial design was so easy to fry by accident, it was a regular occurance.
