Junkers Ju 87 near Sagan, 13 Ju 87s and 26 crew members were lost when they crashed into the ground almost simultaneously. The planes dived through cloud, expecting to release their practice bombs and pull out of the dive once below the cloud ceiling, unaware that the ceiling was too low and unexpected ground mist formed, leaving them no time to pull out of the dive. On 1 September 1939, the Wehrmacht invaded Poland, triggering World War II. "Generalquartiermeister der Luftwaffe" records indicate a total force of 366 Ju 87 A and Bs were available for operations on 31 August 1939. The first
Junkers F 13 It was the world's first all-metal passenger aircraft and Junkers' first commercial aircraft. The designation letter F stood for "Flugzeug", aircraft; it was the first Junkers aeroplane to use this system. Earlier Junkers notation labelled it J 13. Russian-built aircraft used the designation Ju 13. Like all Junkers duralumin-structured designs, from the 1918 J 7 to the 1932 Ju 46, (some 35 models), it used an aluminium alloy (duralumin) structure entirely covered with Junkers' characteristic corrugated and stressed duralumin skin. Internally, the wing was built up on nine circular cross-section duralumin spars with transverse bracing. All control surfaces were horn