That 'airplane' sound is a theremin.

It’s not an airplane. Jimmy Page played a theremin — one of those electronic instruments you wave your hands near — and recorded it with a ton of echo and reverb. That swooping, spacy noise is pure theremin, not a propeller or engine.

Page had a theremin onstage and in the studio. For “Whole Lotta Love,” he ran it through effects to make it sound even more otherworldly. The band was already experimenting with psychedelic sounds, and the theremin fit perfectly into that middle section where the song breaks down.

No planes were harmed in the making of that track.