[2021] Turn off plane engine/ instructor help

There indeed is. Here's how you do it:

Go to the Menu in game. select 'controls' menu. Select 'instructor' tab at the top of the controls menu. For "Throttle Boost Hint", turn it to 'no'. Now, when you turn off your engine (default by pressing ' i ') It should stay off.

Don't forget to have your throttle at 0%