UK SAIL Mark scheme unpacked: a UAS manufacturer’s guide to CAP722K

UK SAIL Mark scheme unpacked: a UAS manufacturer's guide to CAP722K.

A short note before we start: this article assumes some familiarity with the Specific Operations Risk Assessment (SORA) and it's Specific Assurance and Integrity Level (SAIL) scale. If either is new to you, the companion article on SORA-ready UAS design and the UK SORA Compliance page are the faster primers to ready first. Key terms below are expanded on first appearance and listed in Sources and further reading at the end.

What is SAIL Marking?

SAIL Marking is a new UK Civil Aviation Authority scheme, set out in CAP722K published in March 2025, that lets drone manufacturers get their aircraft design formally assessed against the UK's drone safety framework before it reaches an operator.

Under UK SORA, every drone operation is assigned a risk score called a SAIL (Specific Assurance and Integrity Level, from 1 to 6) based on the combined ground and air risk involved. The higher the SAIL, the more robust the technical evidence a drone needs to show so it can be flown safely. Under the SORA methodology, it's technically the operator who applies for permission to fly and who has to gather that technical evidence. As operations become more complex, when operations are increasingly automated, typically when the SAIL increases to 3 or more, a lot of the additional safety compliance requirements are about the UAS itself, how robust and reliable it is, and the evidence to back that claim. At that stage, the operator may not have access to the required design and testing data.

SAIL Marking changes this: a manufacturer can have their drone's design independently assessed by a Recognised Assessment Entity for Flightworthiness (RAE(F), CAP722J) and, where the CAA is satisfied it meets the requirements, receive a SAIL Mark certificate confirming the drone's design meets the UK SORA requirements applicable up to a given SAIL. Operators using a SAIL Marked drone can then rely on that certificate as ready-made proof of technical compliance, rather than building the case themselves from scratch.

When does a SAIL Mark make most sense?

A SAIL Mark is highly relevant for the more complex, higher-risk operations, the ones where the technical evidence UK SORA demands lives inside the drone's design, and an operator simply doesn't have access to it, such as:

• Cases of M2 "Effects of UA impact dynamics are reduced", for example the use of a parachute PRS

• Cases of Containment at medium robustness, for example the use of an independent Flight Termination System FTS

• Compliance with technical Operational Safety Objectives such as OSO#5 "UAS is designed considering system safety and reliability", at SAIL 3 and beyond.

Compliance evidence (testing, analysis, simulation or a design verification report) is data only the designer holds. An operator buying a commercial off-the-shelf drone has no realistic way to produce that evidence themselves.

A SAIL Mark solves this by having the manufacturer build the technical case once and defend it with an RAE(F) and the CAA, so operators can rely on it directly rather than trying to reconstruct evidence about a drone they didn't design.

The commercial implication for a UAS manufacturer is straightforward. A marked aircraft is easier for operators to buy, because it shortens their route to authorisation. An unmarked aircraft can still fly, but every operator carries a heavier documentation burden to get there. Over multiple deployments, that burden becomes a factor in purchase decisions.

Benefits of a SAIL Mark for drone manufacturers: unlock market access

For a manufacturer, the biggest benefit of a SAIL Mark is that it unlocks operations and markets that would otherwise be closed to their drone and their customers under SORA.

The ground risk assessment is one of the most serious barriers under SORA: a UA's characteristic dimension and speed alone often confine operation to remote, sparsely populated areas, unless further ground risk mitigations can be put in place. Operators can implement some mitigations such as operating procedures, ground observation, operating during low traffic hours. But often, that may not be sufficient, and an additional ground risk mitigation point, on the UAS design, is required to enable operations in more dense areas. Often operators can't do that on their own, the evidence needed sits inside the drone's design, not in their own operating history. A SAIL Mark solves this at source: it demonstrates, once, exactly the kind of technical capability that moves a UA out of that remote-only bracket, such as an M2 mitigation reducing the effects of impact, a robust flight termination system, or a design shown to satisfy SAIL 3 and above.

Operators flying that drone can then reach more populated environments and higher-value operations that an equivalent unmarked platform simply can't access. That's a genuine commercial differentiator: two otherwise identical drones can end up serving very different markets depending on whether one carries a SAIL Mark.

It also means the manufacturer stops disclosing sensitive design and test data to every operator and competent authority that asks. The evidence is assessed once, by an RAE(F), and the resulting certificate does the work from then on. Validity is defined in CAP722K and is conditional, typically lasting as long as the configuration and organisational conditions remain within the approved envelope.

The SAIL Mark is optional. When is a SAIL Mark not necessary?

A SAIL Mark isn't for every drone, and skipping it isn't a compliance shortfall, the scheme is optional, so it's simply a commercial choice. It makes least sense for simpler operations: aircraft aimed at SAIL 1 or 2, flown in visual line of sight over moderately populated areas, where most operational safety objectives sit at low robustness and can be met through straightforward self-declaration rather than design-level evidence.

The case is similarly weak for a bespoke aircraft built for one operator, or a handful of them. The value of a SAIL Mark comes from spreading the cost of an RAE(F) assessment across many operators who can then all rely on the same certificate, and that value doesn't materialise when only one customer will ever fly the aircraft; they may as well build the compliance case directly for their own Operational Authorisation.

The same logic applies to a design that's still evolving. A SAIL Mark certificate only covers the exact UAS configuration assessed, and any later change classified as a major modification triggers a fresh application. Pursuing a mark before the design and production process have settled risks paying for an assessment that's out of date before it's even useful. In these cases, it's usually more sensible to wait, or to rely on the standard operator-led compliance route instead.

How the RAE(F) route works

The technical assessment of a UAS design against CAP722K is not carried out by the CAA directly. It is carried out by a Recognised Assessment Entity for Flightworthiness, an RAE(F), operating under CAP722J. The CAA reviews the RAE(F)'s work and issues the SAIL Mark once satisfied.

For a manufacturer this means the primary technical conversation happens with an RAE(F). Their scope is design assurance: the evidence pack, the failure mode analysis, the software development lifecycle records, the containment approach, the human factors argument, all mapped against the UAS design OSOs for the target SAIL. The CAA retains the decision on the SAIL Mark itself.

The CAA publishes an up to date RAE(F) requirement table for Operational Authorisation applicants, which sets out which robustness levels each mitigation must reach at each SAIL. That table is the practical reference for scoping the assessment work.

What to submit, in practical terms

The visible part of any SAIL Mark submission is the test campaign. Flight testing, environmental testing, electromagnetic compatibility, performance characterisation. Most engineering teams scope this work properly during the budget exercise.

The under-scoped part is the documentation. A credible submission may include the failure mode and effects analysis tied to specific OSOs, the software development lifecycle evidence, the hardware acceptance records, the maintenance philosophy and the change control procedure. Each of those documents often needs to exist as a primary artefact, not a retrospective summary written for the assessor.

The manufacturers who will secure SAIL Marks fastest are the ones who will treat documentation as a deliverable from day one of design. The teams who pull the paperwork together at the end consistently will most likely take longer and pay more to get there.

Where the SAIL Mark scheme sits today

The SAIL Mark scheme launched in March 2025. Department for Transport (DfT) & UK Research and Innovation (UKRI) funded a SAIL Mark Certificate programme, and several UAS and accessories are currently undergoing review at the time of writing. The outcome of the SAIL Mark programme should be announced soon, with a number of SAIL Mark certificates delivered at SAIL 2 and 3, for UAS as well as accessories (FTS, PRS) designers.

Manna, the Irish delivery company, announced that they had received a UK SAIL 3 certificate. This is a useful signal for non-UK manufacturers considering the scheme: the pathway is open to platforms already operated in other jurisdictions, provided the RAE(F) can build a defensible bridge to the UK requirements.

No mutual recognition between the UK and EASA at this stage.

There is currently no mutual recognition of SAIL design reviews between the UK and the European Union Aviation Safety Agency (EASA). Brexit removed the automatic recognition pathways that once linked the two regimes, both regulators have only just implemented SORA 2.5, and neither has yet built up the operational return of experience that would justify formal harmonisation. In practice, manufacturers targeting both markets should plan for two separate submissions rather than one combined process.

That said, the underlying technical requirements are now broadly aligned, since both regimes are built on the same SORA 2.5 methodology, so the bulk of the safety case, test data and design evidence can be reused across both. What can't simply be carried over is the review mechanism itself: EASA allows a self-declaration of compliance up to SAIL III (moving to a design verification report, and ultimately a type certificate, at higher SAILs), whereas the UK's SAIL Mark route requires an independent RAE(F) assessment throughout. A manufacturer preparing for both markets is best served by building one evidence package early, then routing it through each regulator's own assessment process rather than assuming either accepts the other's paperwork.

Review pathways by SAIL level

A quick side by side simplified overview of how UK and EASA route design compliance at each SAIL. Full detail lives in our companion article on SORA-ready UAS design.

SAIL Level	United Kingdom (CAA)	European Union (EASA)
SAIL 2 mitigations	Review by an RAE(F) then CAA. Sheltering for UAS above 25kg, M2 mitigation at Medium and High Robustness, Containment at Medium and High Robustness.	Declaration of compliance with Means of Compliance by the designer for Containment Medium and M2 Medium. EASA Design Verification Report (DVR) for High Robustness variants
SAIL 3 UAS	RAE(F) review plus CAA	Manufacturer self-declaration based on EASA MOC compliance
SAIL 4 UAS	RAE(F) review plus CAA.	EASA DVR (mandatory).
SAIL 5 and 6 UAS	RAE(F) review plus CAA.	EASA Type Certificate (Part 21).

When to start the SAIL Mark CAP722K conversation

For new UAS programmes the answer is the same as for the SORA framework itself: at the first design review. The target SAIL, and therefore the eventual scope of any SAIL Mark submission, shapes architectural decisions that are expensive to revisit later. Containment hardware, failsafe paths, software partitioning and configuration management discipline are all cheaper to specify upfront than to retrofit once the aircraft is flying.

For programmes already in flight test, the answer depends on the design maturity. If the aircraft is still flexible at the systems level, the assessment conversation can still shape the route to market. If the aircraft is largely frozen, the conversation shifts towards what SAIL is realistically reachable inside the current configuration, and whether that supports the operator commercial case.

For non-UK platforms already assessed elsewhere, the earliest step is a scoping conversation with an RAE(F) about which of the existing evidence can be recognised, and where a gap analysis is needed.

Frame the aircraft. Prepare the evidence. Engage the RAE(F).

This is the triplet we apply to every SAIL Mark programme. The frame is the SAIL target. The preparation is the evidence pack alongside the build. The engagement is the conversation with the RAE(F), and then with the CAA, on the terms of the recognition itself.

A programme that runs all three in parallel reaches SAIL Mark faster and cheaper than one that defers any of them. A programme that treats SAIL Marking as an afterthought at the end of a design cycle pays for that later, either in review time or in the operator burden that a missing SAIL Mark leaves behind.

If you are considering a SAIL Mark for a new platform, or somewhere in the evidence campaign for an existing one, this is the conversation we help with. The Drone Office works with UAS designers and manufacturers across the UK and Europe on SORA-ready aircraft, SAIL Mark submissions and the supporting documentation that carries them through assessment. The introductory conversation is a no-cost call.

Considering a UK SAIL Mark for your platform?

The Drone Office works with UAS designers and manufacturers across the UK and Europe on SAIL Mark submissions, RAE(F) engagement and the documentation that carries a design through assessment.

Book an introductory call: thedroneoffice.com/contact

Sources and further reading

Primary references for the regulations and frameworks cited in this article. All documents below are public and freely accessible from the issuing authority.

UK Civil Aviation Authority

1. CAP722K, UAS SAIL Mark Policy. https://www.caa.co.uk/publication/download/22716

2. CAP722J, Recognised Assessment Entity Policy. https://www.caa.co.uk/publication/download/22715

3. RAE(F) requirement tables for Operational Authorisation applicants. https://www.caa.co.uk/drones/specific-category/using-the-services-of-a-recognised-assessment-entity-flightworthiness-rae-f/rae-f-requirement-tables-for-oa-applicants/

4. AMC and GM to Article 11, ORS9 Decision No. 46. Operative reference for SORA authorship in the UK. https://www.caa.co.uk/publication/download/22617

5. CAP722, Unmanned Aircraft System Operations in UK Airspace. https://www.caa.co.uk/our-work/publications/documents/content/cap722/

European Union Aviation Safety Agency

6. EU Regulation 2019/947, Implementing Regulation on UAS operations. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32019R0947

1. EASA Easy Access Rules for Unmanned Aircraft Systems. https://www.easa.europa.eu/en/document-library/easy-access-rules/easy-access-rules-unmanned-aircraft-systems-regulations-eu

Internal references

8. The Drone Office companion article: SORA-ready UAS design. https://www.thedroneoffice.com/post/sora-ready-uas-design-a-uas-manufacturer-s-guide-to-easa-and-uk-compliance-in-2026

9. The Drone Office SAIL Marking pillar page. https://thedroneoffice.com/sail-marking

10. The Drone Office UK SORA Compliance page. https://thedroneoffice.com/uk-sora-compliance