What is UK SORA? A plain-English guide to the CAA's drone risk assessment

Drones now inspect power lines across miles of countryside, survey railway lines and carry medical samples between hospitals. The further a drone flies from its pilot, and the closer it gets to people and other aircraft, the more the CAACivil Aviation Authority needs to see before it says yes. In the UK, you make that case through UK SORA.

If you've been told your operation needs a UK SORA authorisation and you're trying to work out what that actually means, this is the starting point.

What UK SORA is

UK SORA stands for Specific Operations Risk Assessment. It's the method the CAACivil Aviation Authority uses to decide whether a drone operation that goes beyond the basic rules can be flown safely. Pass it and the CAACivil Aviation Authority grants you an Operational Authorisation, the document that sets out what you can fly, where you can fly it and the conditions you have to stick to.

UK SORA is the CAACivil Aviation Authority's version of SORA 2.5, a risk assessment method written by JARUSJoint Authorities for Rulemaking on Unmanned Systems, a group of aviation regulators from around the world that includes the CAACivil Aviation Authority. The CAACivil Aviation Authority adapted it to suit UK airspace and UK law, and on 23 April 2025 it replaced the old OSCOperating Safety Case method as the way to apply.

How UK SORA scores the risk

UK SORA looks at the whole operation, meaning the drone, where it flies, how high it goes and who and what is around it. It scores two kinds of risk.

• Ground risk. The chance of your drone hitting someone on the ground and causing a fatal injury if it comes down. It's driven by the drone's size and top speed and by how many people are under your flying area and the safety margins around it. The score is the GRCGround Risk Class, from GRCGround Risk Class 1 (lowest) to GRCGround Risk Class 7.
• Air risk. The chance of your drone meeting a crewed aircraft, such as a light aircraft or a helicopter. It's driven mainly by the type of airspace you fly in. The score is the ARCAir Risk Class, from ARCAir Risk Class-a (lowest) to ARCAir Risk Class-d.

You can bring either score down with mitigations, which are safeguards you can prove you have. Keeping the public out of your flying area, fitting a parachute and keeping the drone in sight are common examples.

The two scores then combine into one number, the SAILSpecific Assurance and Integrity Level, which runs from SAILSpecific Assurance and Integrity Level 1 to SAILSpecific Assurance and Integrity Level 6. Your SAILSpecific Assurance and Integrity Level decides which of the 17 OSOsOperational Safety Objectives apply to you and how much evidence each one needs, covering things like crew training, maintenance, procedures and how the drone was designed. You'll also need to show the drone will stay inside its planned area if something goes wrong, to a standard set by your SAILSpecific Assurance and Integrity Level and by how many people live around that area. The CAACivil Aviation Authority calls this containment. A lower SAILSpecific Assurance and Integrity Level means less evidence to gather and less for the CAACivil Aviation Authority to check.

You apply online through the CAACivil Aviation Authority's UK SORA Application Service, in two stages. In Assessment 1 the CAACivil Aviation Authority checks your SAILSpecific Assurance and Integrity Level, your containment level and any mitigations you've claimed. In Assessment 2 it checks your evidence for every requirement at that SAILSpecific Assurance and Integrity Level, then decides whether to grant your OAOperational Authorisation. One authorisation can cover several locations and several drone models, as long as you show you meet the requirements for each.

The three categories of drone flying

UK drone rules sort every flight into one of three categories, based on how risky it is.

1. Open category. Basic, low-risk flying under fixed rules. You'll usually need to register with the CAACivil Aviation Authority, but you don't need its permission to fly. Broadly, the drone weighs under 25 kg, stays in sight, flies no higher than 120 m (400 ft) and keeps set distances from people.
2. Specific category. Anything that goes beyond the Open category rules. You need an Operational Authorisation from the CAACivil Aviation Authority before you fly, and you can use it for work, for a hobby or for both.
3. Certified category. The highest-risk flying, regulated in much the same way as crewed aviation. More on this further down.

UK SORA sits entirely in the middle, in the Specific category.

Who needs a UK SORA authorisation

The CAACivil Aviation Authority offers two main routes to an Operational Authorisation, PDRA01Pre-Defined Risk Assessment 01 and UK SORA.

PDRA01Pre-Defined Risk Assessment 01 is a ready-made authorisation with fixed limits. It lets you fly a drone between 250 g and 25 kg within sight in towns and built-up areas, up to 120 m high and no more than 500 m from the pilot, keeping 50 m from people who aren't involved (30 m during take-off and landing). It costs £524 a year, suits jobs like roof inspections and photographing buildings, and is currently the only PDRA available in the UK.

If your operation doesn't fit inside PDRA01Pre-Defined Risk Assessment 01, you need a UK SORA authorisation. The CAACivil Aviation Authority gives these as examples of operations that need one.

• Flying beyond visual line of sight, where the pilot can't see the drone
• Flying higher than 120 m (400 ft) above the ground
• Dropping items from the drone
• Flying close to crowds
• Flying close to people with an older drone that weighs more than 250 g and has no UK class mark
• Swarm operations

Drones of 25 kg or more need UK SORA too, because PDRA01Pre-Defined Risk Assessment 01 stops below 25 kg. In practice that covers most of the advanced work drones now do, such as long-distance BVLOSbeyond visual line of sight inspection of power lines, pipelines and railways, drone deliveries and docked drones that fly from a base without a pilot on site.

That applies to hobbyists and businesses alike, because the category depends on the risk of the flight. Whoever applies needs a CAACivil Aviation Authority Operator ID and an operations manual, and the authorisation is issued to that operator. Your remote pilots also need to be competent for the flying you plan, and the CAACivil Aviation Authority's recognised qualifications for this are the GVCGeneral Visual Line of Sight Certificate and the newer Remote Pilot Certificates at levels 1 to 4.

What qualifies a drone for UK SORA

UK SORA doesn't set a weight limit. The two numbers that matter most come straight from the manufacturer's spec sheet.

• Maximum characteristic dimension. The wingspan of a fixed-wing drone, or the distance between the furthest blade tips on a multirotor.
• Maximum speed. The top speed the drone is capable of, as stated by the manufacturer. A drone that can reach 30 m/s counts as 30 m/s even if you only ever fly it at 10.

The bigger and faster the drone, the higher its starting ground risk. A drone weighing 250 g or less with a top speed of 25 m/s or less automatically gets the lowest starting score, wherever it flies.

Flying more than one model? You work out your SAILSpecific Assurance and Integrity Level using the largest size and the highest top speed across all of them, even when they come from different drones.

UK SORA covers drones up to 40 m across and up to 200 m/s (around 450 mph), flying no higher than 66,000 ft. Drones over 3 m or 35 m/s also can't use it over the very busiest areas, those with more than 50,000 people per square kilometre, such as city centres and large events. Anything outside those limits, along with Multiple Simultaneous Operations, flights that need an airspace change and carrying dangerous goods, starts with an email to the CAACivil Aviation Authority at uksora@caa.co.uk.

You don't need a certified drone to apply, but the evidence you'll need about the drone grows with your SAILSpecific Assurance and Integrity Level. At the lower SAILs most of the evidence is about how you operate. From SAILSpecific Assurance and Integrity Level 4 upwards, the parts of the drone that matter for safety need to be designed to a recognised airworthiness standard, which usually means working with the manufacturer.

Going beyond UK SORA: the Certified category

SAILSpecific Assurance and Integrity Level 6 is as high as UK SORA goes. Some operations carry more risk than the Specific category is built for, and they move into the Certified category. Under UK drone law that happens when an operation involves

• carrying people, which is always in the Certified category
• flying over crowds with a drone that is 3 m or more across
• carrying dangerous goods that could pose a high risk to people if the drone crashed.

Your UK SORA scores can also take you there. If your ground risk is still above GRCGround Risk Class 7 after every mitigation you can claim, the operation carries more risk than UK SORA is designed for, and the options the CAACivil Aviation Authority will discuss with you include the Certified category. The CAACivil Aviation Authority can also decide from your risk assessment that an operation can only be made safe enough through certification.

In the Certified category a drone is treated much like a crewed aircraft. The drone's design has to be certified, the operator has to be certified and, where it applies, the remote pilot needs a licence. That's a far bigger undertaking than a UK SORA application, so it's worth knowing early if your plans are heading that way, while there's still time to change the operation.

Which category is your flight in?

Start at the top and work down. If you can tick every box in a category, that category applies to you. If there's a box you can't tick, move on to the next category.

If you're heading for UK SORA, your SAILSpecific Assurance and Integrity Level is the number to find out first. It shapes how much evidence you'll gather, how long the application takes to put together and what the CAACivil Aviation Authority charges. It isn't set in stone either. Where you draw your flying area, how high you fly and which safeguards you can prove can all move it, so it pays to work it out before you commit to a plan.

Quick questions

References

• CAA, Specific Category overview
• CAA, UK SORA-based Operational Authorisations
• CAA, Operations covered by UK SORA
• CAA, PDRA01 overview
• CAA, AMC1 to Article 11, Conducting a UK SORA (ORS9 Decision 46)
• CAA, GM1 to Article 6, Certified category
• JARUS, SORA 2.5 publications