Thanks to Fla-tenor for contributing to this tip.
Have you ever wanted to have a plane start out in a 90-degree dive? or upside-down? You can change the pitch angle of an aircraft (or any object) by loading the mission file in an editor (use Windows Notepad or DOS Edit).
Open a mission file in Notepad. Now, scroll down until you see an object. The line you fiddle with is the "angle" line.
It usually reads "angle 0 0 0"
The first number is the compass heading of the target. 0 is north, 90 is east, -90 is west, -180 is south.
The middle number is pitch. If you change it to "0 90 0" then the plane'll start the mission going straight up! And -90 would be straight down, 0 is level flight.
My guess is that the third numbers represents roll but I haven't played with it yet.
You can also adjust x, y, and z coordinates by adjusting the numbers on the POS line. Although the improved 3D editor in the Pro Mission Creator allows you to place objects with pretty good precision, sometimes a personal touch is required to place an object exactly where you want it (i.e. placing objects where the PMC does not allow them), and this can be done by editing the POS line. You can also use this trick to edit waypoints. For instance, you can place an object or waypoint below 1000 ft, which you can't do within the game because the PMC does not permit it. But edit the POS line yourself, and it will work.
The pos line has 3 numbers, x z y. As you might have guessed, x and y represent the position longitudinally and latitudinally on the map. The numbers vary depending on the map used for the mission. The number in between, z, is the altitude in feet of the object. 0 means the object is on the ground, anything above 0 means the object is in the air. I haven't tried negative numbers, but I don't think it will work.
obj
type TOR.PT
pos 186940 20000 770859
angle 45 0 0
nationality3 4
flags $4017
speed 928
alias -3
controller $80
name Player
skill 2
react $1800 $8000 $0
searchDist 10
wing 2 0
wng 1 0 2048 0