The GEIPAN A/B/C/D framework — how the French programme classifies what it investigates

One of the most institutionally substantive contributions of the continuous French UAP investigation programme — across its GEPAN, SEPRA, and GEIPAN phases — has been the development and consistent application of a four-tier case-classification framework, commonly referred to as the A/B/C/D classification. The framework was developed in the early GEPAN period in the late 1970s and has been applied substantially consistently to all formally investigated cases across the subsequent decades. Understanding the classification framework is essential to interpreting the GEIPAN public case archive, which presents each released case with its assigned classification.

The four tiers

The framework categorises investigated cases into four tiers based on the available investigative evidence and the analytical conclusion reached. Type A cases are those for which a conventional positive identification has been established — the observation has been attributed to a specific known source with confidence. Type B cases are those for which a conventional explanation is considered probable but not definitively established — the most likely source has been identified but the available evidence does not rise to the level of confident attribution. Type C cases are those for which the available evidence is insufficient to support any specific attribution, conventional or otherwise — typically due to limitations in the original observational record. Type D cases are those for which conventional-explanation candidates have been investigated and excluded, and for which no satisfactory explanation is available on the evidence — the cases that GEIPAN classifies as genuinely unexplained.

The distinction between Type C ("insufficient evidence") and Type D ("conventionally inexplicable") is the most institutionally consequential feature of the framework. The two categories produce different analytical conclusions and reflect different limitations on the underlying investigative record.

The Type D subset

Across the operational history of GEPAN/SEPRA/GEIPAN, the Type D subset has consistently represented a small but non-zero proportion of investigated cases — typically in the range of a few percent of the total caseload. The Type D cases are the institutionally significant residual: cases that the French national investigation programme has actively investigated, has applied conventional-explanation candidates to, and has concluded cannot be satisfactorily attributed on the available evidence.

The Type D classification does not, in the GEIPAN framing, constitute affirmative evidence of any specific extraordinary hypothesis. It constitutes acknowledgement that the conventional candidates have been examined and have not produced a satisfactory account. The category is therefore an analytical-honesty mechanism rather than an interpretive claim.

Why the framework matters institutionally

The A/B/C/D framework is institutionally important because it allows the French programme to maintain analytical discipline while engaging substantively with cases that resist conventional explanation. Many other national UAP institutional frameworks have struggled to develop equivalent terminology — the US Project Blue Book "unidentified" category, the UK MoD "no defence interest" closure, and others — that allow institutional acknowledgement of unresolved cases without forcing premature interpretive conclusions.

The framework's consistent application across nearly five decades of French institutional UAP investigation has produced a methodologically coherent case archive in which cases are comparable across periods and across investigative staff. This is one of the structural features of the French programme that distinguishes it from less institutionally stable national equivalents. For specific GEIPAN-investigated cases with their assigned classifications, see the SkyLens UAP files page.

Editorial note: Independent SkyLens analysis of a French institutional UAP case or the GEPAN / SEPRA / GEIPAN investigative framework. The case index linking related releases is on the SkyLens UAP files page.