A top Amazon executive has doubled down on just how serious his company is about using drones to deliver orders to customers’ homes and workplaces.

Yahoo Tech published a new interview yesterday with Amazon vice president Paul Misener, who said that despite skepticism, the Amazon Air Prime program is “very real” and has a “beefed up” team of engineers and robotics specialists tackling the problem. He also revealed a few details about the different types of drones under development and vented some mild dissatisfaction with U.S. regulators over airspace restrictions.

One of the interview’s most interesting tidbits concerns Amazon’s plans to use different kinds of drones for Prime Air. Misener says that a drone prototype shown off in a video in November would be just one of many models tailored for various climates from hot deserts to rainy tropics. There will also, he says, be different models for delivering to skyscrapers and apartments versus suburban homes.

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In response to one of the laziest objections to drone delivery—can’t someone just shoot it down?—Misener’s answer is both simple and insightful: “I suppose they could shoot at trucks, too.” Point being, opportunities for theft and violence surround us every day, but most of us are decent folks (plus, police). As the sight of delivery drones become common, Misener continues, the anxieties that might fuel dronicide will fade.

But Misener also digs in to the much more serious challenges of regulation and airspace. Amazon amzn has previously proposed a ‘layered’ approach to the skyways, with commercial delivery drones operating in a band between 200 and 400 feet, and a 100 foot buffer below commercial jet airspace.

Whether the FAA eventually goes for that, the bigger problem will be how delivery drones interact with noncommercial drones that share their airspace.

For more on drones, watch our video.

Misener says Amazon’s drones will have sophisticated technology for detecting and avoiding obstacles and other drones, and compared the systems to horses that refuse to ram themselves into trees no matter how the rider insists.

But over the holidays, consumers bought an estimated one million drones, and only a handful of models incorporated crash avoidance technology—at prices double or triple those of even high-end sensorless drones.

Even though so-called sense-and-avoid is sure to become more common and affordable, all those ‘dumb’ drones will be in the sky for years to come and represent a real threat to commercial operations. As Misener points out, the FAA has limited ability to regulate amateur drones, which he says “doesn’t make sense.” However, the FAA’s new drone registration requirements suggest it may continue to extend its reach.

Amazon has repeatedly pushed back against the FAA’s regulatory moves—it was Misener who wrote a letter last April that claimed proposed rules would stifle innovation. Now, Misener goes so far as to speculate that regulatory issues involving airspace could delay Amazon’s deployment of Prime Air in its home country.

“Well, we have customers all around the world, of course,” he says. “There’s no reason why the United States must be first.”