Swaab was wounded on the afternoon of September 8, 1918 near Cirey-Saarburg. Having shot down a two-seater, he was about to land at a German aerodrome when he realized his mistake. Enemy fighters scrambled to intercept Swaab's SPAD S.XIII and he shot down two Fokker D.VIIs while making his escape.

On October 23, Swaab shot down a Fokker D.VII that had just destroyed an American balloon. Evidence suggests the German pilot was Max Näther of Jasta 62.

In 1938, Swaab served as technical advisor on the "Dawn Patrol," a Hollywood motion picture starring David Niven and Errol Flynn. He was also a member of the American Cross and Cockade Society.