active runway:

If you can't figure out where to go after receiving taxi instructions from the Ground Controller, you can press Alt-F12 to toggle on the Taxi Path aid. A bright green line will appear on the tarmac to guide you to the active runway.

hot key combinations:

Although the original five aircraft from Flight Unlimited II don't have any autopilot controls displayed on their instrument panels, you can still have full autopilot functionality with them by using the appropriate hot key combinations.

Press A to toggle autopilot on or off
Alt-A for altitude
Alt-H for heading
Alt-N for NAV 1
Alt-S for speed
Alt-V for vertical speed
Alt-W to level wings
Alt-M for instrument approach

trouble trimming:

If you are having trouble trimming your chosen aircraft for straight and level flight, then turn on the autopilot and let it do the work for you. Once you disconnect from it, the airplane should be nicely balanced for hands-off flying