[SmG Bonnie]

1. How do airplanes stay in the air?

[Linamium]

They have jet engines...

[Mohireza]

Guess someone needs to surf the Wikihow

[Skie]

ok. 
First, the airplanes have jet engines that propels it forward

Second, the wings are made in with a curved upper surface and flatter lower surface, creating something known as an airfoil.

Third, the jet engines propelling the plane forward will cause air to split through the wings,increasing air pressure at the lower surface and decreasing air pressure at the upper surface, which then the air accelerates downwards, forming what's known as a lift, which keeps the plane in the air.

[SmG Rexy]

The Jets and wings combined with the air lol