1948 KLM Constellation air disaster

A KLM Lockheed L-049 Constellation airliner (named Nijmegen and registered PH-TEN) crashed into high ground near Glasgow Prestwick Airport, Scotland, on 20 October 1948; all 40 aboard died. A subsequent inquiry found that the accident was likely caused by the crew's reliance on a combination of erroneous charts and incomplete weather forecasts, causing the crew to become distracted and disoriented in the inclement conditions.

Events prior to approach

The aircraft was piloted by Koene Dirk Parmentier, one of the winners of the MacRobertson Air Race, widely regarded as one of the great flyers of the era, and KLM's chief pilot. The co-pilot on the flight was Irish citizen Kevin Joseph O'Brien.

Nijmegen was scheduled to fly from its home base at Schiphol Airport near Amsterdam at 8:00 p.m. CET to New York via Prestwick, with Shannon Airport in Ireland as the alternative stopover point in case of bad weather at Prestwick. The aircraft carried sufficient fuel to divert to Shannon and then back to Schiphol, if necessary. The plane's departure was delayed as additional cargo was loaded for transport to Iceland, which would be an additional stop en route from Prestwick to New York.

The plane eventually left Schiphol at 9:11 p.m., crossed the English coast at Flamborough Head, eventually heading NW at 2320, when it turned almost due South approximately 15 miles ESE of Kilmarnock. The aircraft eventually started its run in towards runway 32 (Prestwick's longest runway and, at the time, its only runway that offered a ground-controlled approach, at 2325 at 1500'.

The weather forecast Parmentier had been given by the Royal Dutch Meteorological Institute at Schiphol had told him that there was some slight cloud at Prestwick, but that it would likely dissipate by the time the Nijmegen arrived. This report was incorrect; the weather at Prestwick was steadily deteriorating, with the weather at the alternative destination of Shannon even worse.

Parmentier believed that there was a strong crosswind, blowing at right-angles to the main runway (Runway 32) at Prestwick of about 20 knots, which might prevent a landing on it. Prestwick had a second, alternative, runway (Runway 26) which was heading into the wind but had no radar-approach system. However, KLM pilot guidelines, drafted by Parmentier himself, forbade a landing at Prestwick in low cloud on the alternative runway.

By the time of approach, Prestwick was under drizzle and a cloud-base that was almost solid at 600 ft, forecast to continue from about 11:00 p.m. onwards, around the time the Nijmegen was approaching the airfield. As the flight had taken off late, they had not picked up the radio message broadcast by Prestwick airfield informing them of this. Parmentier was thus unaware of the deterioration in the weather: were he aware of it he would have been able to divert to Shannon. The routine weather reports broadcast from Prestwick had given a cloud cover of 700 ft. No new forecasts, which would have told Parmentier of the expected decreased ceiling were broadcast. Nor did he know that already that evening two airliners from SAS had turned back rather than attempt a landing at Prestwick.

Inland of the runway was high ground of over 400 ft, but the KLM-issued charts which the crew were using did not mark any land higher than 250 ft. Three miles (5 km) to the north-east of the runway, rising to over 600 ft, were a set of wireless masts. 3 mi inland ran a series of electricity pylons and high-tension cables, the main national grid line for South Scotland, carrying 132,000 volts. However, the error-riddled charts issued by KLM did not have these marked and gave a spot height close by of 45'.