The greatest disaster of aviation industry accidents involved two large commercial aircrafts, Boeing 747 by KLM and PAN AM at Tenerife Airport. NTSB and Netherlands authority reports.

1. KLM flight 4805 and Pan Am flight 1736
Bachelor’s of Aviation Management

2. • The Tenerife airport disaster was a fatal
runway collision between two Boeing 747’s
on Sunday, March 27, 1977, at Los Rodeos
Airport.
• Killed 583 people
• A bomb explosion at Gran Canaria Airport,
and the threat of a second bomb, caused
many aircraft to be diverted to Los Rodeos
Airport
• A dense fog developed at Tenerife, greatly
reducing visibility.
• Result:
• Destroyed both aircraft
• Killing all 248 aboard the KLM flight
• 335 passenger killed from the Pan Am flight.
• Sixty-one people aboard the Pan Am flight,

3. • The civil aviation authorities had therefore closed the airport temporarily after the bomb
detonated and diverted all of its incoming flights to Los Rodeos.
• The official report from the Spanish authorities explains that the controller instructed the Pan
Am aircraft to use the third taxiway because this was the earliest exit that they could take to
reach the unobstructed section of the parallel taxiway.
• The Pan Am crew found themselves in poor and rapidly deteriorating visibility almost as
soon as they entered the runway
• Misinterpretation that they were in takeoff position and ready to begin the roll when takeoff
clearance was received, but not in the process of taking off.
• Both airplanes were destroyed. All 234 passengers and 14 crew members in the KLM plane
died, as did 326 passengers and nine crew members aboard the Pan Am, primarily due to
the fire and explosions resulting from the fuel spilled and ignited in the impact. The other 56
passengers and five crew members aboard the Pan Am aircraft survived, including the
captain, first officer and flight engineer.

4. Pan America World Airways(747-
121)
KLM Royal Dutch Airlines(747-206B)

5. • Sudden fog greatly limited visibility. The
controller tower and the crews of both
planes were unable to see each other.
• Simultaneous radio transmissions, with the
result that neither message could be
heard.
• Use of ambiguous non-standard phrases
by the KLM co-pilot and the Tenerife
control tower.
• The airport was forced to accommodate a
great number of large aircraft, resulting in
disruption of the normal use of taxiways.
a. Diversion of aircraft to Los
Rodeos
 Bomb threat at Gran Canaria International
Airport by the separatist anti-Francoist
Fuerzas Armadas Guanches.
 The civil aviation authorities had therefore
closed the airport temporarily after the
bomb detonated and diverted all of its
incoming flights to Los Rodeos
 Five large aircraft were diverted to Los
Rodeos, the airport is too small to
accommodate all planes.
 After the threat at Gran Canaria had been
contained, authorities reopened that airport.

6. b. Taxiing and take-off
preparations
 The KLM was cleared to taxi the full length of
the runway and make a 180° turn to get into
takeoff position
 The controller asked the flight crew to report
when it was ready to copy the ATC clearance.
 Afterward, the Pan Am was instructed to
follow the KLM down the same runway, exit it
by taking the third exit on their left and then
use the parallel taxiway.
 Initially, the crew was unclear as to whether
the controller had told them to take the first or
third exit.
 There were no markings or signs to identify
the runway exits and they were in conditions
of poor visibility.
 The Pan Am crew appeared to remain unsure
of their position on the runway until the
c. Weather conditions at Los
Rodeos
 Los Rodeos airport is at 633 metres (2,077
feet) above sea level, which accounts for cloud
behavior that differs from that at most other
airports.
 Clouds at 600 m (2,000 ft) above ground level
at the nearby coast, are at ground level at Los
Rodeos/Tenerife North.
 The Pan Am crew found themselves in poor
and rapidly deteriorating visibility almost as
soon as they entered the runway.
 According to the ALPA report, as the Pan Am
aircraft taxied to the runway, the visibility was
about 500 m (1,600 ft).
 Shortly after they turned onto the runway it
decreased to less than 100 m (330 ft).

7. d. Communication misunderstandings
 Immediately after lining up, the KLM pilot advanced the throttles and the aircraft started to
move forward.
 The co-pilot advised the captain that ATC clearance had not yet been given, and Captain
Veldhuyzen van Zanten responded, "I know that. Go ahead, ask.“
 The KLM crew then received instructions which specified the route that the aircraft was to
follow after take off.
 The instructions used the word "take off," but did not include an explicit statement that they
were cleared for take off.
 Meurs (co-pilot) read the flight clearance back to the controller, completing the read back with
the statement: "We are now at take off.“ Captain Veldhuyzen van Zanten interrupted the co-
pilot's read-back with the comment, "We're going.“
 The controller, who could not see the runway due to the fog, initially responded with "OK"
(terminology which is nonstandard), which reinforced the KLM captain's misinterpretation that
they had take off clearance.

8.  The controller's response of "OK" to the co-pilot's nonstandard statement that they
were "now at take off" was likely due to his misinterpretation that they were in take
off position and ready to begin the roll when take off clearance was received, but not
in the process of taking off.
 The controller then immediately added "stand by for take off, I will call you,“
indicating that he had not intended the clearance to be interpreted as a take off
clearance.
 A simultaneous radio call from the Pan Am crew caused mutual interference on the
radio frequency, this caused the KLM crew to miss the crucial latter portion of the
tower's response.
 Due to the fog, neither crew was able to see the other plane on the runway ahead of
them.
 In addition, neither of the aircraft could be seen from the control tower, and the

10. About 70 crash investigators from Spain, the Netherlands, the United States,
and the two airline companies were involved in the investigation.
Facts showed that there had been misinterpretations and false assumptions.
Analysis of the CVR transcript showed that the KLM pilot was convinced that
he had been cleared for take off, while the Tenerife control tower was certain
that the KLM 747 was stationary at the end of the runway and awaiting take
off clearance.
It appears KLM's co-pilot was not as certain about take-off clearance as the
captain.

11. The four overarching categories in
the Swiss Cheese Model are:
• Organizational Influences
• Unsafe Supervision
• Preconditions for Unsafe Acts
• Unsafe Acts

12. • Explosion at Gran Canaria Airport
• Size & Characteristics of Los Rodeos Airport (Tenerife)
• Dense Fog in Tenerife
• Absence of Ground Radar
• KLM 4805 Fully Refuels at Los Rodeos Airport
• Pan Am 1736 Misses Turn
• Personality Traits of Key Personnel

13.  The words “take off” should never be used in an ATC clearance.
 A redundant means should be provided to confirm take off
clearance at
all airports.

14.  All aeronautical communications should be conducted with
precise
standardised terminology. Rigid standards should be applied to
ensure
that all personnel involved in commercial aeronautical
communications are
fluent in English and speak with minimal accent.

15.  Means should be taken to avoid confusion of an ATC clearance
with take
off clearance. This may involve changing the name “ATC
clearance” so
that it is clearly understood to be nothing more than a description
of the
route to be flown.
 Commercial aircraft should not taxi at any airport in visibility
conditions
below 150 meters unless suitable taxi lighting or other visual aids
and
airport ground radar are operational.
 Landing lights should be on, if practicable, whenever an aircraft is

16. Technical Related
 Clearances to move about an airport, especially clearances to
take off
or land, should be clear and unambiguous, and compliance
should be
exact.
“Upon receiving a departure clearance, the KLM flight misunderstood this as
a take-off clearance and began their take-off roll with Pan Am still on the
runway. Had the KLM crew questioned the clearance, or queried the control
tower as to the location of the Pan Am flight, the accident may have been

17.  Flight crew communications regarding airplane safety readiness
should
be open and effective. Each crew member must clearly give and
receive
communication in such a way that the flight safety decisions
represent the
best product of this open, two-way communication.
“The flight engineer then asked the KLM captain, "Is he not clear, then?" The
KLM captain replied, "What do you say?" and the flight engineer reiterated, "Is
he not clear, that Pan American?" The captain responded with an emphatic

18. Common Theme Related
 Deviations from operations or procedures that are considered
normal, or
routine, increase the risks for human errors of all kinds. When it is
necessary to deviate from normal operations, extra vigilance and
strict
adherence to proper procedures should be emphasized.
“A bombing at the Las Palmas airport, the intended destination of both the KLM
and Pan Am flights, as well as many others, caused a diversion to and an
unusual situation at the Tenerife airport. Everyone involved, from each flight
to the air traffic controllers, were forced to compensate for the unusual

19.  Regulatory standards should be sufficiently flexible to allow
deviation in
special circumstances, without compromising safety. Application
of an
appropriate alternative can result in the level of safety intended by
the
regulation.
“A revised Dutch regulation, imposing new limitations on crew duty time,
was discussed in the accident report and was concluded to have had an
influence on the decision-making of the KLM captain. Previous duty time

20. 1. Aircraft crews are highly structured, mechanistic groups known to be
capable of failures of communication and decision-making. The
Tenerife air disaster is a clear example of that. Mechanistic groups
typically perform very well as long as the tasks are fairly predictable
and routine. However, during crisis situations, these trained responses
tend to break down. Nowhere is this more evident than in the air
transportation industry.
2. Accidents due to equipment failures are now thought to constitute just
three to five percent of all airline accidents. The remaining accidents
are attributable solely to human error. Of the accidents attributed to
human error, nearly three quarters of them are due to poor human

21. 3. Authorities at the U.S.A, National Aeronautics and Space
Administration’s Ames Aerospace Human Factors Research
Division also reports that up to 80 percent of all aircraft accidents
are due to a lack of adequate coordination or utilization of
available resources (Cate, 1990).
4. We must continue looking for ways to reduce subjective
decisions on the part of pilots. We can’t take the human factor out
unless we want a system that is completely rigid and inflexible.
Research, study of lessons learned, and application of the
knowledge gained will help reduce the chances of another
Tenerife disaster in the future.