Hydraulics

The Hydraulics are the aircraft's control. The button appears when you are flying any aircraft. It is above the planehack button. It turns on and off your plane's control. When its on, your aircraft has full control. When its off, your aircraft has no control, it just idles. The button says: HYD (status, ON or OFF).

Planehack

To control two planes at once, keep the hydraulics on for your current aircraft, then turn on planehack. To control the other plane, turn off the hydraulics for your current aircraft and turn on planehack. To regain control of your aircraft, turn back on the hydraulics.

Trivia

 * The hydraulics button initially said HYDRAULICS (current status, ON or OFF)