On 18 April 1944, orders were issued to add distinctive markings to the wings and fuselage of all allied aircraft in the ETO to aid ground forces in the recognition of friendly aircraft.
The directive called for five 18-inch wide bands, three white, alternating with two black, to be painted around the fuselage at a point 10 inches ahead of the tail joint, and around the wings at a point 8 inches inboard of the division of the ailerons and the flaps.
The stripes were hastily painted on in the nights preceding the invasion, which was delayed a day, from 5 June 1944 to the 6th, due to weather. The ground crews worked through the nights applying the stripes with brushes.
Due to the success of the invasion, the need for these identification stripes was diminished, and in late June, a directive was issued to remove the stripes from the upper surfaces of the wings and fuselage.
During late-August to early-September 1944, the stripes were removed from the wings altogether, and by December; the stripes were to be removed from the fuselage of the aircraft. Some groups were perhaps a little better than others in removing the invasion stripes as was directed, as it was a low priority in comparison to the normal maintenance required by the planes. This explains why so many photos show the invasion stripes in various stages of wear.
HTH