What exactly is a light-sport aircraft (LSA)? To qualify as an LSA, an airplane must be a maximum two-place, single-engine, fixed-gear machine that weighs no more than 1,320 pounds (1,420 for watercraft). It must have a level, full-power speed of no more than 120 knots, a clean stall speed no faster than 45 knots and a fixed-pitch propeller.