by 32 miles wide at the widest point and covered by ice for most of the
year.

It was originally intended that the flight route south would be over
Ross Island at a minimum of 16,000 feet. From October 1977, with the
approval of the Civil Aviation Division, descent was permitted south of
the Island to not lower than 6000 feet, subject to certain conditions
concerning weather and other matters. However, the evidence is that the
pilots were in practice left with a discretion to diverge from these
route and height limitations in visual meteorological conditions; and
they commonly did so, flying down McMurdo Sound and at times at levels
lower than even 6000 feet. This had advantages both for sightseeing and
also for radio and radar contact with McMurdo Station. Moreover from
1978 the flight plan, recording the various waypoints, stored in the Air
New Zealand ground computer at Auckland actually showed the longitude of
the southernmost waypoint as 164° 48' east, a point in the Sound
approximately 25 miles to the west of McMurdo Station.

The evidence of the member of the airline's navigation section who typed
the figures into the computer was that he must have mistakenly typed
164° 48' instead of 166° 48' and failed to notice the error. Shortly
before the fatal flight the navigation section became aware that there
was some error, although their evidence was that they understood it to
be only a matter of 10 minutes of longitude. In the ground computer the
entry was altered to 166° 58' east, and this entry was among the many in
the flight plan handed over to the crew for that flight for typing into
the computerised device (AINS) on board the aircraft. The change was not
expressly drawn to the attention of the crew. The AINS enables the pilot
to fly automatically on the computer course ('nav' track) at such times
as he wishes.