On Saturday 20 November the party set off on a two-day navigational exercise to cross the Cairngorm Plateau from Cairn Gorm south to Ben Macdui. Because they were very late in starting (it was almost 11:00 when they left Lagganlia) they used the Cairngorm ski lift to get close to the plateau and then, as planned, they separated into two groups - the more experienced group led by Beattie set off and was followed by the group led by Davidson and Sunderland. After crossing the plateau both groups were to descend to the Corrour Bothy at a much lower level in the Lairig Ghru where they would spend the night - sunset was just before 16:00. The less-experienced group of 15-year-olds would then return along the Lairig Ghru while the other group would return by traversing Cairn Toul and Braeriach on the far side of the valley. In case of emergency each group was to go to the Curran shelter high on the plateau. This plan had been approved in advance by the head of Lagganlia, John Paisley, who could forbid unsuitable expeditions.