During the 1950s it became increasingly clear that there was a requirement in Czechoslovakia for a basic-to-intermediate jet trainer that would bridge the wide gap between the then current piston-engine,tailwheel trainers and the new tricycle undercarriage jet fighters.At that time the only way to undertake this transition was the use of two-seat variants of the jet fighters then in service. This was far from ideal and a big leap for new pilots. What was needed was a completely new jet trainer, something that could replace the old piston trainers with a type that would be reliable as well as cost-effective to maintain and operate. The definitive step on Aero's way to mass production of jet trainers took place in Summer 1961 near Moscow: the L-29 Delfin won comparative testing of three different prototypes and was declared the most suitable trainer in Eastern Bloc countries. 

The final production deliveries of the L-29 took place in 1974, when along with USSR and Romania, the Iraqi Air Force received the last of the 38 aircraft it had on order. In total, Aero built 3,665 L-29s, of which 1,943 were produced at Vodochody and the remaining 1,722 completed by LET at Kunovice. At the time this made the Delfin the most successful trainer ever produced worldwide.

Despite the jet trainer having been withdrawn from military service, in many cases replaced by its successor, the Aero L-39 Albatros, many remain airworthy. In recent years, many older, retired military examples have found favour with civilian operators and there are many now leading a new life as warbirds.