Boeing training video of what to do when the window opens during take off. And, how to open the window during flight in case the front windshield is blocked.

https://www.youtube.com/watch?v=bTYT7ERrw_U

I was on a Southwest flight years ago coming into Chicago Midway. Part way thru the descent, an AC pack on one engines burned out, filling the cabin with smoke. The plane went into a slightly steeper than normal descent for 90 seconds - smoke, a diving plane . . lots of screaming and crying. And then something I've never felt on a plane again - a humid and strong wind blowing on my face. The plane levels out, the captain comes over the PA and apologies, says we just dropped below 10,000 feet . . . and he opened the window in the cockpit to blow out the smoke. Except for some stained underpants . . we landed uneventfully 15 minutes later.

Then there are a few aircraft that can do it like old movies. Perfectly safe to fly with the “window” open, and a hell of a lot of fun