Leduc 0.21
 The Leduc 0.21 was a research aircraft built in France in 1953 to refine the practicalities of ramjet propulsion. Initially proposed as the 0.20 it was essentially similar to its predecessor the Leduc 0.10 but scaled up by around 30% with tip tanks added to the wings. Again it was not capable of take-off under its own power and had to be carried aloft and released.