Independence War is a very cool space flight game. It's complex enough to be considered a space flight simulation. IWar is a single-player game, however. [Independence War 2: Edge of Chaos] includes a multi-player game, but without a persistent universe - I haven't played it yet, but I have it on order. Unfortunately, IWar is a bit old now. It's graphics engine works either in software mode, or in gorgeous Glide-only mode. IWar2 will be more up-to-date in hardware support, of course.

Flight Model

IWar's flight model is the gold standard that other games have to beat to impress me.

Independence War neatly solves the problems of travelling around in a game world that encompasses a dozen or so star systems, while modelling realistic distances and providing challenging, manageable dogfighting. It does so by using three different modes of travel.

Normal flight mode

This is a full Newtonian, very nicely modelled flight mode. Your ship has attitude thrusters to yaw, pitch, roll. The big engine in back will let you accelerate until the cows come home. You also have translation thrusters, allowing lateral and vertical sliding, and braking.

Now, full Newtonian physics is perfectly natural to human beings, and would be easy to learn, except that we're not used to being in an environment without gravity or friction. IWar deals with this in way that you might expect people to in real life; they program a computer to help you.

Your ship flies by default with "computer assist" enabled. This does several things:

When you move the joystick, your ship's computer uses the translation and attitude thrusters to make your ship fly almost like a jet plane. Pulling back pitches up, using down-oriented thrusters towards the front of the ship. Left-to-right motion rolls the ship. Etc.
The throttle position is treated as a velocity setting, rather than a thrust setting. If you're going faster than your current throttle setting, forward thrusters apply braking force to try to correct it. Obviously, there's a max velocity setting at the top of the throttle travel. In this mode, flying your saucer-shaped Dreadnought-class ship is easier than a jet in an advanced simulation game. Since your upper and lower translation thrusters are much stronger than your left and right ones, you even get the effect of turning more sharply by banking, just as occurs in a jet because of the lift from the wings. It feels very intuitive.

Once you've mastered your ship, though, you'll often turn the computer assist off for tricky flying, especially in dog fights. The throttle becomes a thrust setting; you can go wicked fast simply by accelerating continuously. (I don't remember ever reaching a limit.) But of course if you're being pursued by someone with more thrust, this is an evasion tactic with a limited window of usefulness!

You can also apply low translational thrust up, down, or sideways. This is useful for docking maneuvers and such. (More on this later in connection with the autopilot.)

Linear Displacement System (LDS) Mode

This is a sort of "warp drive". When you engage the LDS, you hear the system crank up with a whining noise. It takes a few seconds to get underway, and then there's a different background sound to remind you that it's working. Your ship skips through real space, popping in and out of hyperspace (or something like that). It looks and feels just like normal flight - you can't detect the skipping, that's just the background story on it.

The speeds you achieve are amazing. Your throttle scale is exponential! It's pretty much impossible to convoy in this mode without autopilot assistance, because a slight twitch on the throttle has an immense efect. I'd guess that you can cross a solar system in under half an hour at top speed.

You can't collide with anything. (Or at least the probability is so low it never happened to me - and I flew through a lot of asteroid fields this way.) Dogfighting is impossible in this mode. However, opponents can fire LDS suppression missiles which will collapse your LDS fields and drop you to normal flight mode for as long as the missile lasts and is in range.

Capsule Drive

As fast as LDS mode is, it's impossibly slow for interstellar travel. For this, you have the Capsule Drive. This lets you jump from one point to another, but only between points that have a nearly zero gravity field. The only places that qualify in a solar system are LaGrange points, which are specific locations near planetary bodies where gravitational fields cancel out. (Yes, these really exist.) LaGrange points are shown by an overlay on your HUD.

You program your computer for a destination, enter the LaGrange point, and then watch a few seconds of animation travelling through some hyper-dimensional tunnel at high speed. Then you pop out at the other LaGrange point.

For some unexplained reason, you must enter the LaGrange point from a specific direction (indicated by the HUD; it shows it as a circle with an entry and exit side), and you will exit the destination point in a predictable general direction.

Autopilot

IWar has a sophisticated autopilot to alleviate a lot of drudgery. It can...

... dock. (ship-to-ship, ship-to-station)
... 'formate', i.e. lock in formation relative to another ship. (Useful for convoying, especially in LDS mode with its touchy logarithmic throttle response.)
... approach a target. (Navigation point or station. Nav points are pre-programmed according to the scenario you're playing. The autopilot engages and disengages LDS as it deems necessary. It disengages when within 100 meters of the target.)
... match velocity. (Presumably useful for dogfighting. I didn't use it much. This is different from formate, it doesn't control orientation, just thrust.)

You can do all these things manually, but they can be hard. I have successfully docked a few times, just for fun, using the translation thrusters. It's very hard, though.