Hi,
I played both Sopwith I & II to death and back on moms good old XT machine. Sopwith one was almost unplayable, but I became a total master op sopwith II. I recall reaching level 9 (or something) on one occasion, which was two levels beyond the point where your plane flies so fast it becomes impossible to make a looping
I still played this when I had flashy games like hero's quest and so on. Incredibly addictive. Heartily recommended.
Cheers,
Lodewijk