snow-covered terrain, extending ahead for miles. Similarly, the
roof of the solid overcast extended forward for miles. In the far
distance the flat white terrain would either have appeared to have
reached the horizon many miles away or, more probably, merged
imperceptibly with the overhead cloud thus producing no horizon at
all. What the crew could see, therefore, was what appeared to be
the distant stretch of flat white ground representing the flat long
corridor of McMurdo Sound. In reality the flat ground ahead
proceeded for only about 6 miles before it intercepted the low ice
cliff which marked the commencement of the icy slope leading
upwards to the mountain, and at that point the uniform white
surface of the mountain slope proceeded upwards, first at an angle
of 13°, and then with a gradually increasing upward angle as it
merged with the ceiling of the cloud overhead. The only feature of
the forward terrain which was not totally white consisted of two
small and shallow strips of black rock at the very bottom of the
ice cliff, and these could probably not be seen from the flight
deck seats owing to the nose-up attitude of 5° at which the
aircraft was travelling, or they were mistaken for thin strips of
sea previously observed by the crew as separating blocks of pack
ice.

The aircraft had thus encountered, at a fateful coincidence in
time, the insidious and unidentifiable terrain deception of a
classic whiteout situation. They had encountered that type of
visual illusion which makes rising white plateaux appear perfectly
flat. This freak of polar weather is known and feared by every
polar flier. In some Arctic regions in the Canadian and in the
north European winter, it is responsible for numbers of light
aircraft crashes every year. Aircraft fly, in clear air, directly