Navwar (
http://www.navwar.freeserve.co.uk/) is about the only current manufacturer. The aircraft are molded in lead (intended for miniatures wargames) and the line quite extensive--including the Gotha, Staken, AEG IV, HP 0-400, Ilya Murometz and others. Detail is rather plain, but once assembled they are quite sturdy.
A few years back, C-in-C, a now-defunct American company had some nicely detailed lead 1/285 scale a/c. (If memory serves, including Spad XIII, D.VII, Camel, SE5a, Albatros D.V, Dr1, Nieuport 28, E-III, F2B, Halberstadt C-type, and a DH2). Brookhurst Hobbies in the US was carrying their remaindered stock at one point but my e-mails to them went unanswered a year or two ago.