For the past 3 years I've been working on "Linux Air Combat". The design and coding are now stable, with version 5.64. This is a free, open-source, 3d combat flight simulator for LINUX, themed on World War II, and simulating more than 50 different types of WW2 aircraft. Networked, multiplayer missions support both tactical and strategic combat involving destruction of enemy airfields. Here's a screenshot:
And here's my page on itch.io:
YouTube has a lot of video clips about LAC. Here's a short review of a version from about 3 months ago:
And here's a YouTube playlist with a comprehensive review:
I hope you enjoy this. It's published with full, very CLEAN source code that easily compiles, with no need for modifications or tweaking, on all major LINUX desktop distributions. The itch.io download also includes a precompiled binary that is compatible with recent 64-bit versions of Ubuntu LINUX and PcLinuxOs.