The filmography of the movie says that it was released on Dec. 24, 1938.
". . .Aircraft
Howard Hawks assembled a variety of planes in a film squadron to shoot the flying scenes for the original version of The Dawn Patrol. Hawks used rebuilt Nieuport 28 types as the primary airplane for the British squadron, and Travel Air 4000 types (reconfigured for films and popularly known as "Wichita Fokkers") for German fighters, but other aircraft in his small fleet included Standard J-1 types for shots of entire squadrons, some of which were blown up in explosions, and Waterman-Boeing C biplanes for German aircraft destroyed in crashes. The scene in which Scott takes off with Courtney clinging to the wing switches to a shot of a Travel Air 4U Speedwing fitted with a round cowl over its Comet engine to resemble the Nieuports. Stunt pilots included Leo Nomis, Rupert Symes Macalister, Frank Tomick, and Roy Wilson.
1938 director Goulding used much of this footage in the remake to save production costs. For new closeups of airplanes with his own actors, he acquired three Nieuport 28 replicas from Garland Lincoln, a Van Nuys, California, stunt pilot who also recreated World War I aircraft for Hollywood films. Built by Claude Flagg, these "LF-1" types were constructed from Nieuport plans and had many characteristics of the actual aircraft, including upper wing fabric that ripped in dives. In Goulding's production these aircraft also appear in a few scenes of Nieuports taking off, landing, and taxiing. Additional Nieuport 28 types were simulated by Thomas-Morse S-4C Scouts, and two were used in the flying scene in which Courtney and Scott attack the German airdrome. 59th Squadron's airplanes were marked in standard RFC camouflage and national insignia, had the marking "NIEU 24 E" painted on their tail fins, and displayed a cartoon Hornet painted on each side of the fuselage just behind the cockpit.
For scenes at the German airdrome in which aircraft were moved or had engines turning, Goulding used Wichita Fokkers painted black with German markings. His "Pfalzes" had their wings painted in a large and striking red and white checkerboard pattern. Goulding also acquired two genuine Pfalz D.XII fighters for static closeup shots of parked fighters, with at least one re-painted white in a later scene to "expand" their numbers. Actual Nieuport 28 types and Pfalz D.XII types were used much later in the war than the 1915 setting of The Dawn Patrol, and the model 28 Nieuport was not used by the RFC at all, but their familiarity of appearance to American audiences gave a verisimilitude to both films. . ." from Wikipedia.
