Inspired by the example of his glider flying brother Edgar, Dittmar took an apprenticeship at the German Institute for Gliding (DFS). In 1932, flying his self-built glider Kondor, he won a first prize at the Rhön Glider Competition.
Dittmar then became a research pilot. In 1934, he, Hanna Reitsch, Peter Riedel, and Wolf Hirth were members of Professor Georgii's South American Glider Expedition,:65 where in Argentina he achieved a new world gliding altitude record (about 4,350 metres (14,270 ft)). Later the same year, he achieved a new world record for long-distance using a Fafnir II and was awarded the Hindenburg Cup. In 1936, he achieved the first crossing of the Alps in a glider. He then crowned his career as a glider pilot by becoming the first Gliding World Champion after his victory at the first Rhön International Gliding Competition in 1937.
During and after the Second World War, Dittmar worked as an aircraft designer and test pilot. On 2 October 1941, flying the Messerschmitt Me 163A V4 KE+SW, he became the first human to fly faster than 1,000 km/h (620 mph).:175 This record was achieved over the FAI-specified 3-km distance and was measured using an Askania theodolite. Later, on 6 July 1944, he reached a speed of 1,130 km/h (700 mph) in the Me 163B V18 bearing the Stammkennzeichen code of VA+SP, nearly losing the complete rudder surface in the process to flutter. It is unclear, however, if sufficient altitude was attained to make this a true supersonic flight.
- Reitsch, H., 1955, The Sky My Kingdom, London: Biddles Limited, Guildford and King's Lynn, ISBN 1853672629
- Heini Dittmar at the Deutsches Segelflugmuseum.
-  First gliding world champion
- (in German) Käsmann, Ferdinand C.W., Die schnellsten Jets der Welt (Berlin: Aviatic-Verlag GmbH, 1999, ISBN 3-925505-26-1), pp. 17, 122.
- de Bie, Rob. "Me 163B Komet - Me 163 Production - Me 163B: Werknummern list." robdebie.home. Retrieved: 28 July 2013.
- "Me 163." walterwerke.co.uk. Retrieved: 28 August 2010.
- 50 Jahre Deutsche Motorflugzeuge, Seite 8.