SDL Sopwith

sopwith.org, a fan site with lots of details about the original game.
alt.games.sopwith - a (sadly) long-inactive newsgroup about Sopwith, although you can find some interesting discussions from the ’90s if you’re willing to dig through the spam…
The old Sopwith forum from sopwith.org, now long dead and archived…
Sopwith on Mobygames.
“Wild Blue Yonder” aka “The U.S. Air Force”, the song played on the Sopwith title screen and in the game.
Sopwith Youtube Videos: a curated playlist.
Sopwith Camel N6254 RFC, which was recently assigned the civil registration code of ZK-SDL. A strange coincidence… or a reference to this project? The plane is on display in the Vintage Aviation Museum in New Zealand.
Sopwith: the board game! No relation to the PC game, and the gameplay is quite different.

Sopwith’s author, David L. Clark

Sopwith (video game) on Wikipedia.
A selection of articles about Sopwith, Imaginet and BMB Compuscience.
Decoded: Sopwith, MaiZure’s analysis of the Sopwith source code
“The Search for Nostalgic PC Games Digs Out a Forgotten Gem”, by The Secret Aspirant
Memory Cache: Sopwith (transcript; this aired on Australian TV; watch the clip here).
Sopwith review by TheAlmightyGuru.

Sopwith 3 by Jornand de Buisonjé
Sopwith 2002 by Jon Rafkind
Sopwith Camel by Alan Broun
Sopwith Classic Free for Android, by Contact Computers.
YASG (“Yet Another Sopwith Game”) by zlogic (Russian game)
Sopwith IV by Alec Rivers (in alpha?)
Sopwith for PICO-8 by hwd2002
Sheepwith by Iiro Lindell (plus interview with the author where she mentions the original Sopwith as inspiration)
Sopwith Camel Scout by Grigorich.
Sopwith Back by Elemental Systems
Sopwith - WW1 Flight Simulator; Android version by CactooSoftware.
Sopwith remake by Salty Sea Dogs
Sopwith for the Russian Electronika BK0010 microcomputer.

Sopwith VR (mentions the original in the description on Steam)
Triplane Classic aka Triplane Turmoil
Triplane Turmoil II
Airstrike
Artman’s Goplanes!
Biplane Duel for the Amiga (aka Salmon-Pink Max)
BIP!, inspired by Biplane Duel
Sky Fighter (PS3)
Pocket Squadron on Android, by Bombsight Games.
Air Bandits by Insofta Games
Blazin’ Aces by Duncan Bell
GoPlanes by Shawn LeBlanc, inspired by Sopwith. Available for download on the sopwith.org website.
Warplane Quest by Legia Studios
Great Pilots by KeepPlaying Games