IAI, which also produces drones and satellites, has emerged since 2015 as the leader in converting Amazon's growing fleet of Boeing 767 aircraft.
IAI workers have converted about 80% of Amazon's fleet of around 40 aircraft from passenger to cargo use, according to the state-run company.
"We dismantle every part of the aircraft and rebuild as a cargo aircraft," Yosef Melamed, general manager of IAI's Aviation Group, told Reuters, noting workers seal off windows, rebuild cockpits and install larger doors.
Amazon says it expects to have a fleet of 70 aircraft by 2021.