The construction of  Yeşilköy International Airport (1^st part of Office and Terminal Building) in Istanbul which was started by ENKA in 1975 included a total of 60,000 m² of gross construction area, with a closed part of 23,000 m².

The project consisted of construction of airport terminal and its control tower with annual service capacity of five million passengers. The structure of central building and the adjacent office buildings are mainly reinforced concrete. Mushroom slab system has been adapted to accommodate large size air condition inducts, maintaining appropriate ceiling heights, while also reducing the total building volume. The pyramid shaped roof on the 18 m equilateral triangular module over the main block is formed by precast reinforced concrete slabs resting on a steel frame.

After completion of other units, the terminal was to reach a passenger capacity of 20 million per year.

ENKA was responsible for construction of airport terminal and its control tower with annual service capacity of five million passengers.

Reinforced concrete was selected for the construction system. The roof consists of 61 pieces of steel triangles with 18 meter edges. The terminal was also an underground exit. 150,000 m²  of formwork, 48,000 m³ of concrete and 2,500 tons of steel construction material had been used for the construction.