Boarding the seaplane- in Raiders of the Lost Ark (1981)
You can't have an Indiana Jones movie without a "flying across the map" scene, but of course, before you can do one of those you need a plane, and it needs to fly.
For the flying scenes in Raiders of the Lost Ark Industrial Light and Magic built a miniature plane, shot it against blue screen, and inserted it into empty flying plates. When a real life version of the Martin M-130 seaplane in question was found, the production jumped at the chance to use it. Unfortunately it couldn't fly or float.
Instead the dry-docked plane was shot on land, with a ramp, where a few extras and Harrison Ford pretended to board it. Shallow pools of water, placed next to the plane, reflected the sunlight up on the machine, to simulate a water environment.
Then Alan Maley did a matte painting of the surrounding dock, including such details as the name on the plane. A real dock was shot separately and combined with the "dry" footage to complete the illusion. Reflections of the plane in the water were also painted. Another flawless illusion shot from the ILM matte department. Pure movie magic.
Trivia bit: Thanks to the very detailed The Complete Making of Indiana Jones book, we even know what the shot cost: $18.915, including a $11.000 one-day fee for Harrison Ford and a $80 ticket for Steven Spielberg! In all fairness, they also shot the interior of the plane that day.