“Think of it like a motorcycle in the sky,” says Peter Coker, chief executive of Martin Aircraft Co. Ltd., which has spent 30 years developing the Martin Jetpack here. The Martin jetpack is unique in that it is not rocket powered but has a gasoline engine driving twin-ducted fans. The latest P12 prototype, a far sleeker and shinier model than the earlier versions, will allow a pilot to fly for up to half an hour.

New Zealand is taking the prospect of jetpacks in its airspace seriously, even though the product’s price—more than $150,000—means that just a few dozen have been reserved. Most of those are going to overseas customers.

Rex Kenny is manager for special flight operations and recreational aviation at the Civil Aviation Authority of New Zealand. It is pretty much up to him to decide whether jetpacks should be allowed. Part of the debate took off when the aviation official tried to fit jetpacks neatly into existing categories. Is it a helicopter? Is it an aircraft? Mr. Kenny studied the rule book and concluded it is neither.

“It’s a misnomer to call it a jetpack because it is a ducted fan,” says Mr. Kenny. “It’s a lift device really. When we looked at our rules, microlight was the closest,” referring to a lightweight craft for one or two passengers.