From The Internet Movie Plane Database
Alternative English titles: Enemy Agent / Secret Enemy
Boris Karloff (Valdar)
Margaret Lindsay (Helene von Lorbeer)
Bruce Lester (Frank Bennett)
Leonard Mudie (James Yeats)
Holmes Herbert (Arthur Bennett)
Austin Fairman (George Bennett)
Although the home of cabinet minister Arthur Bennett is a hotbed of spies, moles, and double agents, no one knows the true identity of notorious German spymaster Strendler.
(note : most -if not all- of the air scenes are from The Dawn Patrol ).
Doesn’t match with any Gotha products, could it be Friedrichshafen G.III?
Nicknamed Wichita Fokker.
Aircrafts with lots of changes (second cockpit covered for example).
With another engine cowling.
Or Lincoln / Flagg LF-1 replica.
Note the upper wing machine gun despite the two others firing through the propeller disk.