Episode 67 of The Trigan Empire
The Stolen Plans
aka De superjet (Dutch title)
The superjet (Dutch title, translated)
Written by Mike Butterworth
Illustrated by Oliver Frey
The Stolen Plans was originally published in 4 installments in issues 816 (3 September 1977) to 819 (24 September 1977) of Look and Learn magazine.
To date it has not been reprinted in English.
Plot summary (Dutch)
816 817 818 819
MediaFire via British Comics Compilations