An old training video that shows a an airliner with a flight deck side window open is making the rounds on social media. Watching the pilot crack the window like he’s pulling up to a drive thru window might be a little unsettling, but not only will a plane fly fine with an open cockpit window, there are a few situations where a pilot may intentionally open a window in-flight.

Instagram user from Boeing showing pilots flying a B777 with its front windows obscured and cockpit side window wide open.

The noise is astounding but the air is very calm. It almost looks like you can just hang your arm on the window sill like you’re taking a summer cruise in your car.

recalls a friend describing something similar at the controls of a McDonnell Douglas DC-9:

He did it during a ferry flight as a test while flying at 6,000 feet (1,829 m) and 250 knots. He remarked that the most impressive part of it all was that he could slide over and look straight forward out of the window…but that there wasn’t the slightest breeze in the cockpit. The noise level was extremely high, but not one paper so much as fluttered in the cockpit.

The video showing how a pilot deals with an open window during takeoff or even why a pilot could intentionally open a window during flight.

The video shows that in the event that a flight deck window comes open during the takeoff roll, pilots continue flying the plane as normal until getting to a safe position. Then they can close the window. Chief 737 pilot, Ray Craig, explains in the video that the shape of the fuselage forces wind away from and around the window.

As aviation news site Simple Flying , a variety of aircraft types will have these windows as a secondary exit in case of an emergency. If the cockpit door is stuck in an emergency, pilots won’t be stuck on the flight deck. It’s a safety redundancy that comes with some added benefits. Pilots let in some fresh air while on the ground or even to fly a flag during a celebration.

However, cracking open a window can also have additional purpose. In the event that view from the windows is obstructed, such as while flying around ash, then the pilots can descend below 10,000 feet, depressurize the plane and fly from the open window.

While a variety of planes have opening windows like the Airbus A320, Airbus A380, Boeing 737, Boeing 777 and more, some aircraft don’t. Pilots of the Boeing 747 and Boeing 787, for example, have a hatch that they can make an escape from only in an emergency.