Luftwaffe aircraft, in all six positions throughout its deployment in the war, as was regulation before July 1939 for the entire Luftwaffe — these were often displayed without the outermost black "flanks", seemingly making the existing white "flanks" appear to be even thinner than regulation, which through photogrammetric examination of some examples, make the stroke width of the white "flanks" on some He 177 airframes as narrow as 1/80 the length of the core cross from end to end, only one-quarter as wide as the 1/20 regulation width called for on the upper wing Balkenkreuz regulation dimensions. Sometimes the wide-flanked underwing Balkenkreuz would be substituted for the narrow-flank version on some He 177A aircraft, and was already in use on many He 177As in that position. Until 1935, civilian aircraft only had a registration painted on. This was usually the letter D (for Deutschland) national identification letter in use from before 1928, followed by three or four numbers. After 1935, military planes carried, on the fuselage, an alphanumeric four-character Geschwaderkennung code with the Balkenkreuz after the first two characters, always consisting of one letter and one number in a unique combination for a specific Geschwader or Gruppe. The third letter always designated the individual aircraft ID within a Staffel, while the fourth letter designated the Staffel itself within the larger Geschwader or Gruppe unit it belonged to. Camouflage schemes In the Luftwaffe, there were centralized regulations on field camouflage patterns. In practice, these were either amended or ignored. Units in various areas used their own way of painting the aircraft excepting the Geschwaderkennung alphanumeric unit identifiers. Units in the very northern parts of Europe used pale blue wavy lines on a gray background. Night units of both fighters and bombers tended to color their aircraft completely black with a light brown or light gray pattern. This changed in early 1942: night fighters were painted a light gray on the upper surfaces and fuselage/nacelle sides, with light blue undersides, then over-sprayed with either irregular dark gray spots or irregular dark gray lines over all their upper surfaces. The irregular lines were meant to match the intricate patterns of ocean waves (usually called "wave-mirror" camouflage) as seen from the air, especially for interceptions of RAF night bombers over the North Sea. The nighttime skies over Germany usually had some light from either moonlight or even from city lights reflecting upwards into the