Delivery
The last mile, the landing site, and the handover. Payload and route are everything, and the site decides more than the aircraft.
The last mileDrones
Two questions settle almost every drone project. What has to move, and who is underneath while it moves.
Add a gram of payload and you add structure to carry it, motor to lift it, and battery to power the motor. The battery is itself mass, so it needs a little more of all three. The gram is paid for four times before it has flown anywhere.
That compounding is why range collapses as payload rises, and why the curve is not a straight line. A machine that carries two kilos is not a machine that carries one kilo with a bigger battery. It is a different aircraft.
It is also why the first question is never which drone. It is what has to be moved, how far, how often, and what happens on the day the wind is wrong.

Payload
Every published endurance figure is measured with no wind, a new battery and nothing kept in reserve. None of those three conditions exists on an ordinary Tuesday, which is why real routes are planned at roughly half the number in the brochure.
The reserve is not a safety margin that can be spent when the schedule slips. It is the fuel to reach an alternate landing site, and treating it as optional is how an aircraft ends up in somebody's garden.
The types
Four shapes, and the physics that decides which one a job needs.
| Type | Good at | Bad at | Where it fits |
|---|---|---|---|
| Multirotor | Holding still, landing anywhere, simple to operate | Range, and every minute of hovering | Short hops, inspection, photography |
| Fixed wing | Distance per watt hour | Stopping, and needing somewhere to land | Survey and mapping over open ground |
| Hybrid | Taking off vertically and then cruising | Complexity, and carrying two sets of problems | Longer delivery legs |
| Tethered | Staying up indefinitely | Going anywhere at all | A fixed vantage point over one site |
Hovering is expensive and cruising is cheap, and almost every choice on this table follows from that one sentence.

The rules
European drone rules sort flights by risk and not by aircraft size. The open category covers low risk flights below a hundred and twenty metres and needs no permission. The specific category needs an assessment approved by the authority. The certified category is run like manned aviation.
Which category a job lands in is decided mostly by who is underneath. Flying over your own yard, over a road, and over a crowd are three different legal situations with the same aircraft.
That is why the map of where you may not fly gets drawn before the one showing how far you could. A route planned on endurance alone usually crosses something that makes it a different category of flight.
Two jobs
Delivery and inspection pull the design in opposite directions. Each has its own page.
The last mile, the landing site, and the handover. Payload and route are everything, and the site decides more than the aircraft.
The last mileA patrol that measures. What the instrument records, and what it is built not to record.
The roundOr write here
Name, an address we can answer to, and what you are trying to build. You get a reference back straight away.
Those two numbers plus who is underneath settle most of it. We read the record and the rules before anybody quotes an airframe.