Extreme sportsters Fred Fugen and Vince Reffet climbed to the summit of the Jungfrau mountain in Switzerland’s Bernese Alps, one of Europe’s highest peaks at 13,642 feet (4,158 m).

Armed with push-to-talk radios, they then leapt off, and accelerated to catch up with an airplane being flown by pilot Philippe Bouvier, falling in through an open doorway in what the pair described as “the most intense project of [their] careers.”

“You need to have skills, focus and there’s also a lot of work,” the pair said in a statement released by Red Bull. “We had to make the plane safe so we don’t hurt ourselves if we touch it. We also worked on the parachutes so they don’t open too fast in case we touch the plane. But the biggest risk was when we BASE jumped from the cliff. That’s why we wanted to train so much before going to the mountain. In total, we flew into the plane 20 times.”

This is not the first time people have jumped into airplanes, mind you – Joe Jennings achieved it with a plane-to-plane skydive in 2006 with no wingsuit. And Troy Hartmann did the same for MTV in 2011, among others – notably in the pre-GoPro era, so this harrowing footage was captured on giant head-cameras: