IMDB Film Summary:

One minute the New Yorker advertising expert Jim Ferguson (Alex Hyde-White) is at a business party -- the next he finds himself way back in 1917 in a plane fight during WWI. Mr. Raymond (Peter Cushing) explains to him that he has a time-twin to whom he's relocated in space and time whenever one of them is in trouble. So he has to help his twin, biplane pilot Biggles (Neil Dickson),, in his attempt to destroy a Nazi-German super weapon, that could win their war.  Of course it's hard for Jim to explain his sudden disappearances to his fiancée Debbie (Fiona Hutchison). (User Rating:  7.1/10 (85 votes) )
 

From Leonard Maltin's Movie & Video Guide:

Curious, occasionally entertaining sci-fi adventure with Hyde-White inexplicably traveling through time from 1986 N. Y. C. to WW1 Europe...where he assists British flyboy Dickson. Based on characters created by Capt. W. E. Johns. Original British title: BIGGLES.