You will likely get a lot of progress towards this while working on the rest of this game. Heck, you should definitely unlock this naturally if going for Wing Commander (1000 hours of flight time). But if you're just itching to get it over with, here is what I did:
World Map >
Departure: KLGA (Laguardia, New York) - GATE (GATE 1 -- GATE SMALL)
Arrival: KJFK (Kennedy Intl, New York) - GATE (GATE A 14 -- GATE MEDIUM)
Plane: Textron Aviation Cessna 152
Once you load in, let the AI Co-Pilot take over and they will automatically start the plane, taxi, take-off, land, taxi, and park (if they don't crash somewhere along the way). Took about 15 minutes each time and got 4-6% added to the tracker each time it completed (if the AI Co-Pilot didn't crash).
Long and short is this is likely not the easiest or most efficient way to get this, but it's how I got it. The point is to find a larger airport, click on it, and choose "Zoom For Details" (Under Set as Departure/Arrival). You want to choose a Gate/Ramp that is far away from a runaway to increase the amount of time the pilot has to taxi. Same goes for the arrival airport.
I'm sure there is a better, longer route combination to maximize the amount of taxi time per flight. Feel free to share and I will update the solution! Let me know if I can do anything to improve this guide!