March 27 is a sombre day for the aviation industry, as it marks the anniversary of the most fatal plane accident in history, which took the lives of 583 people and injured an additional 61.

The deadly crash involved not one, but two aircraft, and the location of the accident was the airport runway itself.

On March 27, 1977, two Boeing 747 passenger jetliners collided in a horrific accident which resulted in a loss of life on a scale never before seen in the aviation industry.

KLM Flight 4805 and Pan Am Flight 1736 met their tragic end at 5:06 pm GMT in thick fog conditions on the runway at Los Rodeos Airport in Spain’s Tenerife (later renamed Tenerife North–Ciudad de La Laguna Airport).

Both Boeing 747s were originally not intended to land at Tenerife’s Los Rodeos Airport – their planned destination was Gran Canaria Airport in Las Palmas, reports the Daily Star.

However, a bomb explosion at the latter earlier in the day led to them being diverted to Los Rodeos, the only other nearby airport capable of accommodating a 747.

What transpired on that ill-fated day

Los Rodeos, a small airport typically handling light aircraft, was congested with rerouted flights and had limited parking for planes the size of the Boeing 747.

Adding to this, KLM’s captain, Jacob Veldhuyzen van Zanten, was growing increasingly agitated with the delays and he and his crew needed to return to Amsterdam after dropping off the passengers at Las Palmas once the threat had been neutralised.

The Dutch government had recently amended crew duty time restrictions, and a substantial delay at Tenerife threatened to push the crew of KLM Flight 4805 considerably beyond their permitted duty hours, which would trigger significant complications, both operationally and financially.

Indeed, on seeing the airport in Tenerife, senior pilot Zanten was reportedly heard saying: “I’ve seen postage stamps bigger than this place. Now we’re going to get boxed in here, goddammit.”

Presumably, Zanten carried considerable responsibility – he was KLM’s leading pilot, the head of safety and KLM’s chief flight instructor, his image featured prominently in the airline’s marketing which stated: “KLM. From the people who make punctuality possible.”

Zanten had made the choice to refuel the aircraft before departure, and it was the combination of catastrophic miscommunication, poor weather conditions, and a full fuel tank that ultimately resulted in the devastating collision which saw the now-defunct Pan American’s Flight 1736 still manoeuvring on the runway while KLM Flight 4805 attempted take-off.

Captain Zanten erroneously believed he had received clearance to take off, propelling the KLM aircraft down the runway at take-off speed, directly into the taxiing Pan Am plane.

The cockpit voice recorder (CVR) recovered from Pan Am’s Black Box following the crash captured the aircraft’s captain, Victor Grubbs, exclaiming: “There he is!” when he spotted the KLM craft’s landing lights through the thick fog. When Grubbs noticed the KLM plane hurtling towards them at full takeoff speed, the captain’s chilling final words were: “There he is… look at him. Goddamn, that son-of-a-b**** is coming!”, while first officer Robert Bragg shouted: “Get off! Get off! Get off!”

In a bid to evade a collision, Grubbs applied full power to the Pan Am’s throttles and performed a sharp left turn towards the grass, however, by the time the KLM pilots spotted the other aircraft, they had already surpassed their V1 speed, making it impossible for them to halt.

The KLM pilots attempted lift-off in desperation to avoid a crash which resulted in a tailstrike instead. Although the KLM craft was briefly airborne, its fuselage scraped over the PanAm’s rear fuselage, obliterating it and severing off the aircraft’s tail.

The KLM 747 continued to fly and crashed out of control 150 metres further ahead, sliding for another 300 meters down the runway, while simultaneously bursting into flames due to the impact with the runway, which caused its full load of fuel to combust and ignite instantly into a fireball that took several hours to extinguish.

The collision claimed the lives of all 248 people on board the KLM flight, including the crew, while 335 of the 396 people on board the Pan Am flight also perished.

All 61 survivors from the Pan Am were seated in the forward section of the aircraft, with one survivor subsequently stating that sitting in the nose of the plane was probably what saved his life. All five people in the Pan Am flight’s cockpit – the three-man crew and two off-duty employees who were riding in the jumpseats – miraculously survived.

When KLM executives first received word of the catastrophic crash, they had reportedly attempted to contact KLM’s Golden Boy, Captain Zanten, with the hopes of dispatching him to Tenerife to assist the investigation team, not realising that he was the captain of the flight that had been involved in the accident and had perished in the crash.

The false assumptions and miscommunications before the accident between the pilots, cockpit crew and Air Traffic Control tower led to a complete overhaul of international airline regulations, transforming them forever.

Following the Tenerife crash, air traffic controllers were required to use standardised English phrases and had to make decisions by mutual agreement. In a significant improvement in crew resource management, guidelines were established which allowed pilots to challenge the captain with less difficulty.