The AV-8B Harrier II is a single-engine, ground attack fighter jet. This is my first VTOL jet, so apologies if there are any issues of taking off or landing, plus I also tried to make the cockpit interior as accurate as possible with the real thing while also keeping an eye on its performance cost and there are a lot of switches and buttons that have no purpose so don't bother testing to see what they do. Here are the instructions you MUST follow in order to perform a VTOL take-off:

First, turn on activation group 7, this will activate a gyroscopic stabilizer and some RCN nozzles to make your VTOL take-off more steady.

Second, adjust the angle of the VTOL nozzles to face downwards (since it starts off facing behind).

Third, once the VTOL nozzles are facing downwards, slowly increase your throttle it should get off the ground once throttle is at 40% (if you increase the throttle too quick it will likely flip the jet and inevitably crashing it)

Lastly, once you reached a high enough altitude, quickly adjust the VTOL nozzles to back to its original position. From there you can increase your throttle without worry. Once the jet is flying forward you can turn off the gyroscopic stabilizer.
Note: It's very hard to land without exploding. Good luck with that.

Functional AG groups:
AG 8=Start up/Stop engine
AG 7=Gyroscopic stabilizer and RCN nozzles
for vertical take-off and landing.
AG 6=Master Arm switch (Engage/disengage
secondary weapons).
AG 2=MCPD lights (just for esthetic purposes).

Weapons:
• Minigun/GAU-12 Equalizer
• 2 Anti-ship missiles (Each can one shot ships)
• 2 AGM-65 Maverick missiles (credits to
Greasytortle for its model)
• 4 AIM-9X Sidewinder missiles (modelled it
and customized it myself).

I guess this is all, if I forgot to add something I'll edit this description.