Acadmy/Minicraft has a small line of 1/72 scale WWI injection molded kits available. All are excellent quality and are very affordable. In fact they seem to be the least expensive of all currently in-print kits. Their line includes: Sopwith Camel, Spad XIII
Aeroclub is an English manufacturer of aftermarket add-on parts (white metal) and kits. They have injection molded kits for the Bristol Scout D and the Aviatik Berg D-I as well as a vac-u-form kit of the Se2a.
Airfix has the largest line of currently available injection molded WWI kits in 1/72 scale. Unfortunately the quality of their kits is spotty. Some are good and some are very poor. The following list should help you avoid the really bad ones.
ESCI has stopped production of military models. Buy any and all available ESCI kits. All are of high quality, easy to assemble with great decals and are easilly re-sellable. Their kits include: Albatros D-III, Fokker DVII, SE5a, Neuport 17c, Sopwith Camel Spad XIII and all 6 in one boxed set (Red Barron's Flying Circus)
ERTL is rumored to have the molds for the ESCI WWI aircraft line. I'm trying to encourage modelers to write them to convince them to re-release these kits.
Manufacturer of vac-u-form kits in all scales.
Merlin produced short run injection mold kits that included decals. I'm pretty sure they are out of business now. The kits tended to be on the low end of the quality scale: Thick parts, flash and surface defects. They did however produce kits with very interesting and esoteric subjects including: Vickers F.B.5 Gun Bus, DH-5, Pfalz Triplane and Sopwith Dolphin.
Miekraft is a small U.S. company that does limited run injection molded kits. Some kits have lead parts. I have tried their models - which are mostly planes that no other manufacturer does. They tend to be very difficult to assemble and have a LOT of flash, bubbles and goiters on them. I would not reccomend them unless you are REALLY desparate for the particular plane they are offering. They add and discontinue kits often so if you find a plane you are interested in from them, buy it immidiately. It may not be around for long.
Small company that produces limited run injection molded and also resin kits. I have built some of their injection molded kits and find them to be of fairly high quality for limited run kits. They usually take some hand work to insure proper part fit but isn;t that what modeling is all about? Past releases have included: Sopwith 1 1/2 Strutter, Pfalz D-IIIa, Pfalz D-XII, Sopwith Salamander and Roland D-VIb.
Ragwings produced short run resin kits in 1/72 scale.
Revell has re-released some of their WWI models. They are all high quality although some (Neuport 28 especially) are more difficult to assemble than kits from other manufacturers. Their current line includes: Fokker DRI, Fokker DVII, Sopwith Camel, Neuport 28 and Spad XIIIC. Also look for out of print kits from Revell manufactured as far back as 1960: Sopwith Triplane, Fokker E-III, Moraine Saulnier N Type and Airco DH-2. All of these are excellent and are not available anywhere else.
This eastern eourpean company has recently started releasing some excellent injection molded kits in 1/72 scale. These are highly reccomended.
Tom's Model Works
Manufacturer of resin and limited run injection kits in all scales.