The pressurised cabin of the Junkers EF 61 was based on that of the Junkers Ju 49. The EF 61 was one of the few German high-altitude bomber and reconnaissance projects before World War II. The project started in September 1935 and the maiden flight took place on 4 March 1937, but on 19 September of that year the EF 61 V1 was destroyed in a crash.[1] The second prototype EF 61 V2 was ready in late 1937 but also crashed in December 1937, even before high-altitude testing had started. After that the project was abandoned.[1] The project eventually led to the high-altitude reconnaissance aircraft of the Junkers Ju 86 type in World War II.