The L-159 ALCA is designed for the principal role of light combat aircraft (single-seat L-159A variant) or light attack jet and advanced/lead-in fighter trainer (two-seat L-159B and T variants). Design of the L-159 was derived from the L-39/59 in terms of aerodynamic configuration but a number of changes were made to improve its combat capabilities. These include strengthening of the airframe, reinforcing of the cockpit with composite and ceramic ballistic armour and enlargement of the aircraft's nose to accommodate the radar. Compared to the L-59, the number of underwing pylons was increased from four to six, and a new hardpoint under the fuselage was added instead of a GSh-23L cannon.