Hi Mattias,
I mainly use a set from an old copy of Wargames Illustrated called "Snoopy vs the Red Baron" they're very simple but good fun.
There's also "Fokkers over Flanders" - I think by TTG, so may be out of print.
If you've a hex printed cloth you could try a boardgame such as "Richtoffen's War".
I've heard good things about "Check your Six!" but not played it - I don't know if anyone has backdated it from WWII to WWI.
Hope that helps
vT