Flight Unlimited III was the third and last of the Flight Unlimited series of General aviation flight simulators created by Looking Glass Studios, released in 1999. It included ten user-flyable aircraft in total, and several new features.

One of the most significant new features was the new weather engine. Before a flight the user could generate and manipulate weather fronts, which would then change dynamically while flying. The simulator also included the Raytheon Beechjet 400A. In previous versions, only small- to medium-sized propeller-powered aircraft were included. The Beechjet added a fast jet to the line-up, with a glass cockpit, GPS, an autopilot and a working weather radar using the new weather engine.

As with Flight Unlimited II, the simulator concentrated on one small but highly detailed part of the USA, in this version Seattle. It was once again sourced from USGS satellite photos and real-life elevation data. Outside of the Seattle area, covering more of the Pacific West, was a less detailed area called the outer terrain region.

Other features from Flight Unlimited II include 3d cockpits (although still without working dials), more realistic crashes, water landings, challenges and flight lessons.

If the user had Flight Unlimited II, the high-resolution San Francisco scenery could be installed, making flights between there and the high-resolution Seattle area possible.

The simulator also came with a program called the Flight Unlimited Editor (FLED), which allowed the user to edit the simulator's scenery. This is still one of this simulator's great strengths - it has a free, built-in scenery editor. Anybody can create their own airport, scenery package or just place a few model objects wherever they want. If saved as a scenery 'package', users can upload to the internet (via Avsim.com or similar) and other users can share in the experience. One user (Chris Low from the UK) has created huge super-sets of packages covering entire regions. These substantially improve the flying experience. There are also currently hundreds of extra models available for users to experiment with.