Why do planes take off into the wind?
Wind flowing over the wings gives extra lift, so an aircraft facing the wind needs less runway and speed to take off or land.
The idea
An aircraft lifts off when air moving over the wings is fast enough. If the aircraft faces into the wind, the wind already provides some of that speed, so the aircraft needs a shorter run and lands more slowly relative to the ground.
Headwinds, tailwinds and crosswinds
A headwind blows against the aircraft’s direction and helps. A tailwind pushes from behind and makes the run longer, so airports avoid it. A crosswind blows from the side, and every aircraft type has a limit it can handle.
Why airports switch runways
When the wind turns, the airport changes to the runway pointing most nearly into it. That is why you may see all the traffic suddenly start using the other end of the same runway.
Watch for it
If the wind has changed and the planes are suddenly queuing at the opposite end of the runway, the airport has switched direction.