During an interview on “Late Night with Seth Meyers,” actor Gerard Butler detailed a stressful day of filming on the set of his new movie “Plane.” In the action flick, Butler plays a tough pilot who at one point is working on the landing gear of a plane.

“I’m sticking my hand in between these two wheels, kind of pretending that I know what I’m doing,” Butler said. “Every time I bring my hands out, they’re covered in blood and green fluid, right? And I’m like, ‘I don’t know what this green fluid is.'”

Actor Gerard Butler stars in a new 2023 movie called “Plane.” Getty Images

Turns out it was a synthetic fluid that was “essentially phosphoric acid,” the actor said. When he went to rub the sweat off his face, the fluid transferred to his skin.

“Suddenly, it’s in my throat,” Butler said. “It’s in my mouth. It’s up my nose. It’s in my eyes. It’s burning my face, and I mean burning.”

According to a 2021 article from Spartan College of Aeronautics and Technology, some synthetic types of hydraulic fluid used on plane landing gear are made from a compound “derived from an alcohol and phosphoric acid.” It can be dyed green (or purple or amber) so that it’s identifiable.

“The airline pilots that were there watching go, ‘No!'” Butler said.

The burning sensation ultimately lasted for hours, but “was great for the sequence.”

You can watch Butler’s appearance below: