The three largest categories provide insight into possible explanations for plumes. First, when Stage 1 events were transmitted to the study team, pre-production operations were excluded from reporting at the request of the partners (likely due to ongoing regulatory discussions). During Stage 2 analysis, ≈20% of plumes on partner production facilities were aligned with pre-production operations, some of which are known to have periodic emissions large enough to be detected from aircraft. All of these are likely detections of known pre-production operations. Note that while reported implies that emissions were included in regulatory reporting, this study had insucient data to analyze whether total reported emissions were accurate.