Tenerife Airport Disaster – A Tragic Collision of Two Boeing 747s

The Tenerife Airport disaster, which occurred on 27th March 1977, remains the deadliest aviation accident in history, with 583 fatalities. This catastrophic event unfolded when two Boeing 747 aircraft collided on the runway at Los Rodeos Airport (now Tenerife North Airport), part of Spain’s Canary Islands. The accident involved a KLM Royal Dutch Airlines 747, registration PH-BUF, and a Pan American World Airways 747, registration N736PA. Both aircraft were preparing for takeoff under conditions of reduced visibility caused by heavy fog, contributing to the miscommunication and procedural breakdowns that culminated in the fatal collision.

This incident underscores the critical importance of clear communication, adherence to protocols, and the profound challenges posed by adverse weather conditions in aviation.

Overview of the Incident

The KLM flight, operating as KL4805 from Amsterdam, and the Pan Am flight, PA1736 from Los Angeles, were both diverted to Los Rodeos due to a terrorist bombing at their original destination, Gran Canaria Airport. Along with many other flights, the two 747s were forced to wait at Tenerife until Gran Canaria could reopen. The high volume of diverted aircraft created congestion on the small airport’s single runway and limited taxiways.

After several hours of waiting, the two flights were cleared to return to Gran Canaria. However, due to the lack of available taxiways, both aircraft had to use the single runway for taxiing and takeoff, with the Pan Am 747 instructed to taxi down the runway and exit at the third taxiway, while the KLM 747 was instructed to take off after receiving clearance.

The stage was set for disaster as heavy fog reduced visibility on the ground to nearly zero. The situation was further exacerbated by ambiguous communication between the air traffic control tower and the two aircraft. Misunderstandings led the KLM flight crew to believe they had been cleared for takeoff, while the Pan Am aircraft was still on the runway, resulting in the collision.

Key Factors Contributing to the Collision

Several key factors contributed to the Tenerife disaster, each compounding the challenges faced by the flight crews and air traffic controllers:

1. Reduced Visibility Due to Fog: The thick fog on the ground severely limited the pilots’ ability to see other aircraft or identify runway markings. This forced both KLM and Pan Am crews to rely entirely on radio communications for their situational awareness.

2. Runway Congestion: Los Rodeos was not equipped to handle the large volume of diverted flights. The lack of adequate taxiways forced the use of the runway for taxiing and takeoff, creating a hazardous situation where aircraft had to share the same piece of pavement in poor visibility.

3. Miscommunication: The radio communications between the KLM crew, the Pan Am crew, and air traffic control were fraught with ambiguity. Crucially, when KLM’s Captain Jacob Veldhuyzen van Zanten radioed that his aircraft was “ready for takeoff,” the tower responded with a conditional clearance, instructing them to wait for further confirmation. However, due to simultaneous transmissions from the Pan Am crew, this message was not heard clearly by either the KLM crew or air traffic control, leading to confusion about the actual clearance status.

4. Human Factors: The accident was also influenced by human factors, including decision-making under stress. KLM’s captain, a highly respected and experienced pilot, may have felt pressure to take off quickly due to his duty time limits, potentially contributing to his decision to initiate the takeoff before receiving final clearance.

Collision and Immediate Aftermath

At 17:06 local time, the KLM 747 began its takeoff roll without full clearance, while the Pan Am 747 was still taxiing on the same runway. The Pan Am crew, having missed the correct taxiway exit due to poor visibility, was unable to vacate the runway in time.

As the KLM aircraft accelerated down the runway, the Pan Am crew spotted the lights of the approaching jet and attempted to turn sharply to avoid a collision. However, it was too late. The KLM 747 became airborne momentarily but crashed into the upper fuselage of the Pan Am aircraft, tearing off its roof and igniting a massive fire.

The KLM aircraft was instantly destroyed upon impact, with all 248 people on board perishing in the fire. Of the 396 people on the Pan Am flight, 335 were killed, primarily due to the ensuing fire. However, 61 survivors, including the captain, were able to escape through the broken fuselage before the flames fully engulfed the aircraft.

Runway Safety and Procedural Breakdown

The Tenerife disaster is a tragic example of how multiple small procedural breakdowns can compound into a catastrophic event. At its core, this incident illustrates the critical importance of strict adherence to air traffic control procedures and the role of clear, unambiguous communication in ensuring runway safety.

1. Conditional Clearances: A key factor in the miscommunication was the use of conditional clearances, where the KLM crew interpreted the phrase “take off” as a final clearance rather than a pre-clearance instruction. The lesson from this is the importance of absolute clarity in air traffic control instructions, particularly in situations where multiple aircraft are using the same runway under low-visibility conditions.

2. Runway Incursion: The collision was effectively a runway incursion, where two aircraft occupied the same runway at the same time. This highlights the need for strict protocols to prevent incursions, including the use of surface movement radar systems, which were not available at Los Rodeos at the time.

3. Situational Awareness: Both flight crews were operating under severely reduced situational awareness due to the fog. In modern aviation, improved technology, including ground-based radar and cockpit displays, helps ensure that crews have real-time awareness of other aircraft and runway conditions, reducing the risk of similar accidents.

Emergency Response and Aftermath

The emergency response at Los Rodeos was hampered by the scale of the disaster and the limited resources available at the airport. Firefighting teams faced immense challenges in controlling the fires that engulfed both aircraft, and the thick fog further complicated rescue efforts. Despite these difficulties, 61 survivors from the Pan Am flight were rescued, many of whom were seated in the front section of the aircraft, which was not directly impacted by the collision.

In the wake of the disaster, the aviation industry implemented several important changes to improve runway safety and communication protocols. These include:

1. Standardised Phraseology: The use of non-standard or ambiguous phrases in radio communications has been minimised through the adoption of standardised phraseology in air traffic control instructions. This ensures that all flight crews, regardless of their native language or level of experience, interpret instructions in the same way.

2. Crew Resource Management (CRM): The Tenerife disaster highlighted the importance of effective teamwork and communication within the cockpit. As a result, Crew Resource Management (CRM) training became a mandatory component of pilot training worldwide, focusing on improving decision-making, leadership, and communication among flight crews.

3. Runway Safety Technology: Airports have since invested in advanced ground radar systems, such as Airport Surface Detection Equipment (ASDE), to monitor aircraft movements on runways and taxiways, even in low-visibility conditions. Additionally, the installation of runway status lights provides visual cues to pilots about whether it is safe to enter or cross a runway.

Conclusion

The Tenerife Airport disaster serves as a somber reminder of the catastrophic consequences that can arise from a combination of miscommunication, procedural lapses, and adverse weather conditions. In the years since the tragedy, the aviation industry has made significant strides in improving runway safety, communication protocols, and emergency response capabilities.

As the deadliest accident in aviation history, Tenerife continues to influence how pilots, air traffic controllers, and ground crews are trained to handle complex and potentially dangerous situations. The lessons learned from this disaster have undoubtedly saved countless lives, ensuring that the tragic events of 27th March 1977 are never repeated.