Why do we open window shades during takeoff and landing?

What's the reason behind keeping window shades open when a flight takes off and lands? And why do only some airlines require it? Here's the answer.
AOL

AI probe of aviation close calls leads FAA to limit how helicopters can fly around busy airports

Air traffic controllers will now use radar to actively track helicopters when flying through the flight paths of planes taking off and landing at busy airports, the Federal Aviation Administration ...

How fast do airplanes fly during take off and landing?

Curious about how fast planes go when they take off and land? Explore real speed ranges for commercial jets.
CNN

This vertical take-off gyrocopter could ‘replace helicopters’

A vertical take-off and landing aircraft first flown 60 years ago is being revived, with the aim of offering a cheaper and greener alternative to modern helicopters. “For years we have been looking ...