The Condon Report's optical and radar chapter summarizes the 1954 BOAC observation, discusses possible visual explanations and states that no radar contact was obtained.
It is the key technical secondary source and corrects later retellings that add radar confirmation to a visual-only public record.
The chapter is a later analysis, not raw contemporaneous flight data. It preserves witness and weather discussion but cannot determine the formation's physical size or origin. Original source: https://files.ncas.org/condon/text/s3chap05.htm