zipline's "platform 1" is an airplane, and "platform 2" is a quadcopter shaped like an airplane. https://www.flyzipline.com/technology

So they should have much better efficiency than typical quadcopters

Depends on perspective. You could say it's a glider with a quadcopter bolted underneath for VTOL capabilities.

What is a drone to you? If you are only thinking about multicopters when you hear that word then yes, those are not efficient and probably never will be.

But the term commonly refers to all unmanned aerial vehicles.

For example a Global Hawk unmanned aircraft can fly 14,000 nautical miles and remain aloft for 42 hours. They are by definition very efficient. That is a drone.

On the other end of the spectrum The Spirit of Butts' Farm crossed the atlantic with 118 US fluid ounces (3.5 L) of fuel. It was flying for ~39 hour and 1,881.6 mi (3,028.1 km). That is about 2045 mile per gallon if I count it right. That is very efficient, and of course since the aircraft was unmanned it is a drone.

These are representative of the kinds of drones and aircraft relevant to the context of this post?

Moreso than the quadcopter you probably have in mind.

> For example a Global Hawk unmanned aircraft can fly 14,000 nautical miles and remain aloft for 42 hours. They are by definition very efficient. That is a drone.

Wow - this is what they are planning to use to deliver packages?

If so, unit economics will never work, regardless of cargo.

They use fixed wing aircraft, yes.

Do not want what global hawk is delivering