Most of these stunts are legit on-the-edge-of-your-seat harrowing, but the payoff is always worth it.
The clip comes from one half of the YouTuber duo Venus & Nightmare -- Nightmare, specifically -- who recently shared an awesome three-minute montage of him doing various stunts with various planes. It's really great.
You might have noticed the title, Feather II. The video's actually a sequel to a previous montage, also by Nightmare, called Feather, which was released back in July and consists solely of Mallard stunts. Check it out, it's also pretty good:
Man, I can't wait for that PC version.