Junkers Ju 87 with the Ju 87 A-0, the B-1s were returned discreetly to the Reich. The experience of the Spanish Civil War proved invaluable - air and ground crews perfected their skills, and equipment was evaluated under combat conditions. The Ju 87 had not been tested against numerous and well-coordinated fighter opposition; this lesson was learned later at great cost to the Stuka crews. All Stuka units were moved to Germany's eastern border in preparation for the invasion of Poland. On the morning of 15 August 1939, during a mass-formation dive-bombing demonstration for high-ranking commanders of the Luftwaffe at Neuhammer training grounds
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