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How Do Air Taxis Fly into a Big Airport?
Using Detroit's airport as an example: the Class B airspace, approach corridors and wake turbulence an eVTOL has to avoid, and how holding points and turn radius shape a route.
An electric vertical takeoff and landing (eVTOL) aircraft could take you from downtown Detroit to the airport terminal in a dozen or so minutes. Joby and other companies are already flight testing prototypes. Before a service like that can run, someone has to work out where a new kind of aircraft can fly near a hub airport whose airspace is already busy with airliners.
A paper I worked on looked at that question, using Detroit Metropolitan Airport (DTW) as the test case.
What restricts the airspace
Major US hub airports sit inside Class B airspace, and you need a clearance to enter it. Its shape is often compared to an upside-down wedding cake: the floor gets lower closer to the airport, and the innermost layer reaches the ground. At DTW, everything within 8 nautical miles (about 15 km) is Class B from the surface up to 10,000 ft. Between 8 and 10 nautical miles, the floor rises to 2,500 ft.
Airliners land by following instrument approach procedures lined up with the runway, and those procedures come with obstacle clearance surfaces that keep them safe in cloud. Other aircraft have to stay out of those areas.
Wake turbulence adds another constraint. A wing producing lift sheds a spinning vortex from each tip. A large aircraft’s wake lingers for a while, and a small aircraft that flies into it can be rolled, so controllers apply specific spacing behind heavy aircraft. An eVTOL is far smaller than an airliner, and a widebody that has just passed is a real hazard for it.
The gaps under the airliners
Once all of that is mapped, the space left over is patchy. NASA’s urban air mobility concept of operations calls it interstitial airspace: the gaps beneath the Class B floors and between streams of instrument traffic, which few aircraft use.
When we overlaid historical flight tracks on a 3D map, airliners were concentrated in the approach corridors and on the upper Class B shelves, and the low-altitude band below was mostly empty. The routes in the paper keep eVTOLs beneath the airline traffic, a bit like giving bikes their own lane next to the cars.
Where to wait
Aircraft near an airport often have to wait before landing. An eVTOL runs on batteries, so a long wait becomes an energy problem, and a holding point has to meet two conditions. It should be over open green space with nobody living below, so the aircraft can set down if energy runs short, and it has to be close enough for tower controllers to keep it in sight.
We compared two places to hold. North of the airport, the eVTOL sits behind the airliner stream and gets more wake exposure, but reaching the terminal only means crossing a runway that is not in use, which a letter of agreement signed in advance could cover. Beside the runway, wake exposure is lower, but the eVTOL has to cross an active runway, so a controller must issue a clearance and wait for a gap in arrivals and departures.
One option costs safety margin and the other costs controller workload. The paper does not choose for the airport. It sets out both costs, and the choice depends on which one the airport cares about more.
Turn radius
Drawing a zigzag on a map is easy, but an aircraft needs room to turn. Turn radius is speed divided by turn rate. At 90 knots (about 46 m/s) and the standard rate of 3° per second, a full circle takes two minutes and the minimum turn radius is about 884 m. If waypoints are too close together or the angle between legs is too sharp, the route cannot be flown.
To catch that while a route is being drawn, I wrote a point-mass kinematic model and a web tool. You drag waypoints on a map, the backend checks straight away whether the route is flyable, and you can replay it on a 3D globe from the control tower’s view.
My take
After this project, I think whether air taxis get into big airports depends largely on whether they can fly within the existing airspace rules and air traffic control procedures. That system has run for decades, and eVTOLs will have to learn how it works before they can find usable space in it.
The paper was accepted to ICAS 2026. Details of the study and the web tool are on the project page.