Using a public restroom is never ideal. (Unless it’s the ultra-clean facilities at convenience store chain Buc-ee’s.) But there’s something even worse than venturing into a bathroom at a bar or even a port-a-john: An airplane bathroom. You have all the non-amenities of public toilets with the bonus of turbulence.

Fortunately, there’s an optimal time to go.

Former flight attendant Susan Fogwell spoke with Reader’s Digest about the best strategy for going to the lavatory at 20,000 feet. According to Fogwell, passengers have one ideal window: After boarding but before the plane takes off.

Why? “The lavatories are cleaned by cleaners before every flight,” Fogwell explained. That ensures you get a restroom that hasn’t been ravaged by other travelers. And because the plane is still grounded, you won’t have to deal with turbulence while handling your business.

But what happens when everyone thinks this is the ideal time to go? Most likely, they won’t. Passengers boarding are more focused on finding their seats and getting settled than hitting up the bathroom.

If you find yourself in need of relief once the plane is in transit, try to time it just before drink service. Once beverages start being consumed, you’ll likely have people outside the stall. Plus, you don't want to be trapped by the beverage cart in the aisle when you try to return to your seat post-elimination.

No matter when you go, consider yourself lucky you weren’t there for the pioneering days of aviation. Long before the luxury of jets, pilots and passengers usually had to settle for a cardboard box. And now that you know that fun fact—and when you should be heading to the restroom—check out some things you no longer see on planes, discover why plane windows have tiny holes in them, and read up on common misconceptions about flying.

[h/t Reader’s Digest]

This article was originally published on www.mentalfloss.com as The Best Time to Use the Bathroom On an Airplane, According to a Flight Attendant.