From OSC to UK SORA: Our Transition and BVLOS Roadmap

The way UK operators earn permission for complex drone work has changed at its foundation. The Operating Safety Case (OSC) — the document that underpinned higher-risk Operational Authorisations for the best part of a decade — has been retired, and the UK Specific Operations Risk Assessment (UK SORA) has taken its place. Angell Surveys has operated under an OSC-based Operational Authorisation for the past nine years. That authorisation runs to its expiry in March 2027, at which point we transition to UK SORA. This article explains what SORA is, how the CAA’s latest updates shape it, why the change matters, and how our transition sets up a clear roadmap to routine beyond-visual-line-of-sight (BVLOS) operations.

What changed, and when

On 23 April 2025, the Civil Aviation Authority (CAA) stopped accepting OSC applications. From that date, UK SORA became the method for assessing risk and applying for an Operational Authorisation in the Specific Category — the category that covers most professional survey and inspection work beyond the constraints of the Open Category.

Existing OSC-based authorisations were not cancelled. If you hold one, it remains valid until its expiry date, and variations can still be made against it until then. Any new application or renewal, however, must be built on SORA. That transition arrangement is precisely the position Angell Surveys occupies: our current Operational Authorisation, granted on the OSC methodology, remains in force until March 2027, and our renewal will be our first submission under SORA.

The framework has continued to mature since it was introduced. UK SORA is based on the internationally recognised SORA 2.5 methodology developed by the Joint Authorities for Rulemaking on Unmanned Systems (JARUS), adapted for UK use. The CAA’s Decision No. 60 (ORS9 No. 0060), which comes into force on 1 October 2026, adopts revised Acceptable Means of Compliance (AMC) and Guidance Material (GM) for the UK SORA that align the framework explicitly with SORA 2.5. In practice, operators are working towards a settled, internationally consistent standard rather than a moving target.

How UK SORA actually works

SORA is not a form to fill in. It is a structured method for reasoning about the risk of a specific operation and demonstrating that the mitigations in place are proportionate to that risk. The assessment produces a single rating — the Specific Assurance and Integrity Level (SAIL) — that then dictates how much evidence and rigour the authorisation demands. The logic runs in stages.

Ground risk is assessed first. The intrinsic Ground Risk Class (iGRC), on a scale of 1 to 10, is derived from the aircraft’s dimension and speed and the population density beneath the operation. Strategic mitigations can then reduce it: sheltering (M1A), operational restrictions such as reducing the population at risk (M1B), ground observation (M1C), and measures that reduce the effect of an impact, such as a parachute (M2). Applying these in sequence yields the final Ground Risk Class.

Air risk is assessed in parallel. The Air Risk Class (ARC) describes the likelihood of encountering a crewed aircraft in the operating volume, on a scale from ARC-a (minimal) through ARC-b (low) and ARC-c (medium) to ARC-d (high). Strategic mitigations can lower it to a residual ARC.

The final Ground Risk Class and residual Air Risk Class are then consolidated into a SAIL, from 1 to 6. The higher the SAIL, the more demanding the requirements. SAIL drives the robustness expected of the operation’s Operational Safety Objectives (OSOs) — a defined set of safety requirements covering operator competence, procedures, aircraft design and maintenance, and crew training, each rated as not required, low, medium or high robustness according to the SAIL. UK SORA 2.5 works to a consolidated set of up to 16 OSOs.

Two further concepts complete the picture. Containment — the technical and operational measures that keep the aircraft within its defined operational volume, and account for the adjacent area where it could come down after a loss of control — must be demonstrated to a low, medium or high standard depending on the operation. And tactical mitigations, applied in flight, address the residual air risk: for visual-line-of-sight work this is a documented deconfliction scheme, while for BVLOS it means meeting a Detect and Avoid (DAA) requirement. It is this last element that makes SORA the gateway to BVLOS.

What our transition involves

Nine years of operating under an OSC is not a standing start. The OSC discipline required us to document our operating procedures, emergency responses, maintenance regime, crew competency and risk assessments to the CAA’s satisfaction, and to keep that evidence current through successive renewals. Much of that safety architecture maps directly onto what SORA asks for — the OSOs, in particular, formalise the same operational disciplines an OSC operator has been practising for years.

The transition is therefore a re-expression of a mature safety case in a new, more structured language, not a rebuild from nothing. Between now and our March 2027 expiry we are mapping our existing operations onto the SORA methodology: establishing the ground and air risk classes for our typical survey and inspection profiles, evidencing the relevant OSOs at the required robustness, and defining the containment and tactical mitigations for the operating volumes we work in. Approaching a renewal deadline with the SORA package already prepared — rather than starting it late — is the difference between continuity of operations and a gap in authorisation.

Why SORA is the better framework

For operators and clients alike, the move to SORA brings real advantages over the bespoke OSC it replaces:

• Proportionate by design. The SAIL rating scales the burden of evidence to the actual risk of the operation. A lower-risk survey is not held to the same standard as a high-risk urban BVLOS flight, and the applicant can see exactly where a mitigation would move the rating.
• A common, transparent language. Because every operation is described in the same terms — GRC, ARC, SAIL, OSOs — clients, insurers and the regulator can all read a risk case the same way. That transparency is difficult to achieve with a free-form OSC narrative.
• Internationally aligned. UK SORA tracks JARUS SORA 2.5, the same methodology underpinning the EASA framework. Operators building competence in SORA are building competence against a global standard.
• A designed path to BVLOS. SORA does not treat BVLOS as an exception to be argued for from first principles. It provides an explicit route: identify the air risk, meet the Detect and Avoid requirement, evidence containment, and the operation becomes assessable on its merits.

How this underpins our BVLOS roadmap

Removing the visual-line-of-sight tether is the single biggest step-change available to a survey and inspection business. BVLOS turns a series of short, line-of-sight sorties into continuous corridor and area operations — longer linear assets covered in one flight, sites surveyed without repositioning the crew, and inspection ranges that simply are not reachable while the aircraft must stay in sight.

The CAA has set out how it intends to get there. Its Future of Flight BVLOS Roadmap (CAP3182), published in October 2025, presents a staged set of operational scenarios “from today to 2027 and beyond,” with the explicit aim of integrating drones into shared airspace iteratively rather than through segregated corridors or one-off special provisions. The roadmap’s early pathway — the Atypical Air Environment (AAE) — covers BVLOS operations conducted close to infrastructure such as power lines, railways, wind farms and similar environments, where the presence of crewed aircraft is inherently low. That pathway maps almost exactly onto the sectors Angell Surveys already serves: rail corridors, utilities and water networks, renewable-energy sites and highway structures.

UK SORA is the engine that makes each step of that roadmap accessible. Progressing from line-of-sight work, to BVLOS in atypical air environments, and ultimately towards more integrated operations, is — in SORA terms — a matter of managing the air risk down to a residual class the mitigations can support (ARC-b for scalable operations, with ARC-c environments requiring approved DAA solutions and electronic conspicuity as the airspace architecture matures). Establishing our authorisation under SORA in 2027 is the foundation the whole roadmap is built on: it gives us the methodology, the evidence base and the regulatory relationship to add BVLOS scope incrementally, starting in the atypical air environments where our sector work naturally sits.

What this means for our clients

For the organisations that commission our surveys, the headline is continuity and capability. Our OSC-based authorisation keeps us fully operational through to March 2027, and our SORA transition is planned around that expiry so there is no interruption. Beyond it, SORA gives clients a risk case they can read and rely on in the same terms their own advisers and insurers use — and it puts a structured, CAA-recognised route to BVLOS within reach for exactly the kind of linear and access-constrained assets our clients need surveyed.

The regulatory groundwork is not the visible part of a survey, but it determines what is possible. Building our operations on SORA now is how we make routine, longer-range, beyond-line-of-sight capture a deliverable service rather than an aspiration.

Frequently asked questions

What is the difference between an OSC and UK SORA?

An Operating Safety Case (OSC) was a bespoke safety document an operator wrote to justify a complex operation to the CAA. UK SORA is a standardised risk-assessment methodology that produces a Specific Assurance and Integrity Level (SAIL) from the operation’s ground and air risk, and sets proportionate requirements from that rating. Since 23 April 2025 the CAA has no longer accepted OSC applications; SORA is the route for new and renewed Specific Category Operational Authorisations.

Is Angell Surveys’ current authorisation still valid?

Yes. Our Operational Authorisation was granted on the OSC methodology and remains valid until it expires in March 2027. Existing OSC-based authorisations continue in force until their expiry date; only new applications and renewals must be made under SORA. Our renewal in 2027 will be our first SORA submission.

Does SORA allow BVLOS operations?

SORA is the framework through which BVLOS operations are assessed and authorised. It requires the operator to characterise the air risk and satisfy a Detect and Avoid requirement, alongside containment and the relevant Operational Safety Objectives. The CAA’s Future of Flight BVLOS Roadmap (CAP3182) sets out how BVLOS is being enabled in stages, beginning with atypical air environments close to infrastructure.

What is a SAIL?

SAIL stands for Specific Assurance and Integrity Levels. It is a rating from 1 to 6, derived by combining the final Ground Risk Class and residual Air Risk Class of an operation. The SAIL determines how robust the operation’s mitigations and Operational Safety Objectives must be — a higher SAIL demands more rigorous evidence.

If you are planning survey or inspection work that may call for Specific Category authorisation, get in touch with the Angell Surveys team to discuss how our operations are structured.