The mystery deepens still further, were that possible ...
The results that rank "the 50 busiest airlines operating at Heathrow from April to June this year" strangely omit any details for Icelandair, MEA and Egyptair, all of whom maintained two daily flights throughout those three months.
And yet the likes of Croatian (9 flights per week) and China Southern (a single daily flight up to the beginning of June) are included.
Go figure, as our American cousins say.