We simply don’t know if the Northwest Passage has been relatively ice free before the 1978 satellite data started being collected. But we do have two different BBC reports, in two different years, each claiming the Passage was ice free “for the first time”. Before 1978 we don’t know. It is pure guesswork. But given that the planet has been much warmer than today, in the past, it is likely the Passage has been ice free on many occasions.