Pardon me if I've mentioned this before. There was a great anecdote in one of the late-great Robert Serling books about this back in the 60s. The L188 Lockheed Electra also had a window in the lav. A little old lady entered the lav, did what one does in there and exits. The window was equipped with curtains, don't know about the A220. They are at cruising altitude, mind you.

The Stewardess routinely checks the lav and finds a safety pin closing the two parts of the curtain closed!

"Very bright moon observed today at FL350."

I’ve never thought about it, but yes, a window would be nice, I think that it would make the cubicle seem larger.
Good idea!

At least no one can look in as far as I know. Lots of natural light even in the washroom. The main thing is that this is the "greenest" aircraft in the world. It burns 25% less fuel than it's competitors with similar load factors. I know it is the most quiet airliner that I have ever flown in. Its a great aircraft for all parties concerned.

This window is so you can see where your waste goes after you flush 😂

The window is nice to have, but it could encourage people to spend more time in the lavatory and create a waiting line. More important than the window to me is that the lavatory seems fairly spacious, especially compared to what’s being put into the 737 MAX series.

I'd rather look out the window to get a view at turd-y thousand feet :) 💩

It might be a cure for constipation if you are flying through a thunderstorm.

Should add a lot of fun for those jokesters who might just think it's great sport to stand in front of the window and flash folks before departures.