The L-39 two-seat training jet plane is intended for flights in regular and complex meteorological conditions at day and night time, as well as for acrobatic flying. As for its design, it is a cantilever all-metal monoplane with a trapezoidal low wing. The tail unit of the airplane consists of a trapezoidal keel with an elevator, fixed on the tail of a fuselage. The chassis of the airplane consists of three wheels, including the nose wheel. The main chassis legs are retracted into the wing, and the front leg - in the fuselage nose.

Pressurized cockpits are in the front part of the fuselage. Cockpits are equipped with oxygen supply- and air conditioning systems, thus enabling normal crew operation at high altitudes and allowing to easily withstand the permissible operating G-loads, if pilots wear special harness and use a special equipment. There are ejection seats in the cockpits, enabling to do emergency crew escape. A cockpit canopy is pressure-tight with a single layer glazing, the back-folding parts can be thrown off under abnormal condition by pyrotechnical systems.

Emergency, radio electronic and radio/radar equipment of the airplane ensures airplane piloting at day and night time under complex meteorological conditions.