wow, you are a magical person! I am in awe! bravo!!!!
were i to guess your techinique, short of throwing the plane in the air and taking pics with a highspeed shutter (ergo no blur), I'd also have to guess clear fishing line edited out in post production, or some sort of bluescreen/green screen mask layered over existing shots. am i anywhere close?
Or, as you said, your plane really flies, or you're a great magician!
I love your work!