Urban Aeronautics faces several hurdles. "Ducted fans have been around for years," says Bob Behler, a retired Air Force general who once flew medevac aircraft and now works for the MITRE Corporation, which conducts technical research for the government. "They're very efficient, but reliability is questionable with vectored thrust." Nevertheless, Behler says that ducted-fan aircraft are great for urban operations. "You've got to have something that travels slowly and can maneuver around obstructions," he explains. He remains concerned, however, about not having a medical attendant with the patient.
Frankel-Yoeli agrees, up to a point. "For regular evacuation, it's certainly not the preferred means," she says. "But if the casualty is in critical condition and you have no other means of getting them help, it's not a difficult question." The biggest obstacle, she contends, is psychological. "The problem is overcoming the natural fear of entering a vehicle without a pilot."