Miroslav Hajn was a chief designer at ČKD-Praga

CKD-Praga

ČKD-Praga was a Czechoslovakian aircraft manufacturer. The company was founded in 1915 as an engine manufacturing company, under the designation Praga. The company started designing aircraft in 1930–31 when the designers Pavel Beneš and Miroslav Hajn came to ČKD-Praga from Avia. Their first...

, one of the largest engineering companies in the former Czechoslovakia

Czechoslovakia

Czechoslovakia or Czecho-Slovakia was a sovereign state in Central Europe which existed from October 1918, when it declared its independence from the Austro-Hungarian Empire, until 1992...

 and today's Czech Republic

Czech Republic

The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....

.

Hajn first was a founder and chief designer at Avia

Avia

Avia is a Czech aircraft and automotive company notable for producing biplane fighter aircraft, especially the B-534, and trucks.- History :...

, along with Pavel Beneš

Pavel Beneš

Pavel Beneš was a chief designer at ČKD-Praga, one of the largest engineering companies in the former Czechoslovakia and today's Czech Republic....

, in 1919. The two began repairing planes in a workshop within the complex of an old sugar factory in Prague

Prague

Prague is the capital and largest city of the Czech Republic. Situated in the north-west of the country on the Vltava river, the city is home to about 1.3 million people, while its metropolitan area is estimated to have a population of over 2.3 million...

. One year later, they designed their first two-seater plane: the Avia BH-1

Avia BH-1

|-See also:...

. From 1923 to 1925, the two developed the Avia BH-7

Avia BH-7

|-See also:-References:* Němeček, V. . Československá letadla. Praha: Naše Vojsko.*...

, BH-9

Avia BH-9

|-See also:-References:* Němeček, V. . Československá letadla. Praha: Naše Vojsko.*...

, and BH-11

Avia BH-11

|-See also:-References:* Němeček, V. . Československá letadla. Praha: Naše Vojsko....

 monoplanes, launching the era of biplane fighters. The BH-11 won the Coppa d' Italia prize. Three years later, their Avia BH-21

Avia BH-21

|-See also:...

 fighter was considered one of the world's best planes.

In 1930, Hajn and Beneš came to ČKD-Praga. The first aircraft they designed was the Praga E-39 in 1931.