The nine-passenger F.3X (as the F.121 was also known) with huge high-mounted wings, deep slab-sided fuselage and four 134kW Hispano-Suiza 8Ac engines in tandem pairs, won the 1923 French Grand Prix des Avions Transports and 500,000 francs. Four flew on the Farman airline's Paris-Brussels-Amsterdam route from 1926 and Danish Air Lines used a few between Amsterdam and Copenhagen. Four even uglier F.4X six-passenger aircraft followed, each with three uncowled 223.5kW Salmson Az.9 engines, two engines mounted (as before) above the landing gear on the lower stub wings and one in the upper fuselage nose. These served with Compagnie Internationale de Navigation Aerienne (formerly CFRNA) along with the more attractive Caudron 81 and Potez 32.

Interestingly military Jabirus also appeared as prototype heavy bombers and escort fighters with stepped noses, each carrying twin Lewis guns on a Scarff ring in a nose cockpit and light bombs in a fuselage bay. Heavier bombs or, a torpedo could be carried under the fuselage.