That is an incredible and prime example of Pilot error.
This kind of thing makes me sick.
Why did he even want to go so bad anyway??
Both flights supposed to land at Las Palmas on Grand Canary Island that day, but a local separatist group had exploded a bomb in the terminal there, so they were diverted to Tenerife.
It was already a busy Sunday at Los Rodeos, and the addition of flights diverted from Las Palmas made things pretty chaotic by midday. The weather was pretty crummy, and getting worse.
The KLM captain had hoped to keep his pax on board at Los Rodeos until Las Palmas was reopened, but the delay grew longer, so after much further delay finding parking for KLM 4805, they were disembarked. He then decided to take on fuel.
By the time Las Palmas Airport was re-opened, the Pan Am crew had already put in almost 11 hours that day, and the KLM crew was closing on 9 hrs. The KLM crew still had to get to Las Palmas, then return the 747 to Amsterdam so that it could meet the next day's schedule.
By the time KLM 4805 got their taxi clearance, just after completing the fuel check, they'd been delayed over 2 hours at Los Rodeos. Van Zanten, itching to get the hell out of there, apparently started "tuning out" the radio calls, and missed the critical information that Pan Am 1736 was still taxiing on Runway 12.
Here are some excerpts from the transcript:
ATC: Clipper 1736, report leaving the runway.
KLM 4805 had been cleared to taxi on the runway also, and turn to hold in postion for takeoff on runway 30. At 17:05:28, van Zant started throttling up as soon as the takeopff checklist was complete...KLM F/O: Wait a minute; we don't have an ATC clearance...
The KLM captain, a senior training pilot who had more recent sim time than flight time, pulled the throttles back, realizing his oversight.KLM Capt: No, I know that; go ahead, ask.
ATC: KLM 4805, you are cleared to the Papa beacon, etc....
note that this is not a takeoff clearance, it's a departure procedure clearance- the words "cleared for takeoff" are not used.
Before the controller even finished the clearance, van zant said "Yes", and started advancing the throttles again.KLM F/O: ...cleared to the Papa beacon...we are now at take-off.
Apparently the words used by the F/O were indistinct; perhaps the controllers did not think they'd be rolling when it was clear that the Clipper was still back-taxiing...but they tried to check- unfortunately, so did the Pan Am crew. they queried KLM 4805 at the same moment, cancelling each other out. so van Zant didn't hear the reminder at first.
What they tried to say: ATC: stand by for take-off; we will call you...
(Pan Am 1736 thought the transmission was for them...)Pan Am F/O: No, uh... we are still taxiing...
All that was heard on the freq was a squealing sound, however, so this additional error went unnoticed. ATC acknowledged the Pan Am transmission and asked them to report clear... meanwhile, KLM 4805 was still accelerating down 30- straight at the Pan Am plane.KLM Flight Engineer: Is he not clear, then?
KLM Capt: What did you say?
KLM F/E: is he not clear, that Pan Am?
KLM Capt: Oh,
yes.
The F/O seemed to agree, so the F/E dropped the matter. The Dutch 747 continued accelerating, with another 747 sitting right in front of them, lost in the fog.
To their credit, the Pan Am crew now realized things were rather uncertain, although they did not know KLM 4805 was actually taking off, so they decided to do something.
Pan Am Capt: Let's get the hell out of here.
Pan Am F/O: yes, he's anxious, isn't he?
Pan Am F/E: Yeah, after he's held up... now he's in a rush.
Pan Am Capt: There he is... look at him... that... that... S.O.B. is coming...
Pan Am F/O: Get off! Get off! Get off!!
Pan Am Cpt. Grubbs firewalled it and tried to turn left, off the runway. At that very moment, the Dutch F/O called V1.
Four seconds later, as they began to rotate, the KLM crew saw the Pan Am plane trying to roll clear.KLM Capt: Oh...
Van Zant tried to pull the 747 off the ground early in an attempt to miss the other plane; the tail struck the runway and left a 60- foot-long "streak of of metal" on the pavement. KLM 4805 became airborne briefly, but it was too late. An engine and the landing gear of the KLM 747 clipped the top of the Pan Am 747's fuselage.
The two aircraft were not all that terribly damaged by the initial collision, believe it or not: the reason so many died was because of the fire, and the fact that there was a slightly-too-long delay in scrambling rescue equipment and personnel because the noise in the fog was though at first to be another terrorist bomb, probably involving a fuel tank at the edge of the field.
The fog and congestion hampered the crews' eventual arrival at the wreck site, which turned out to be two wreck sites...causing more precious seconds to be lost in deciding what to do.
Out of the 396 Pan Am crew and pax, only 70 survived.
Because the KLM ship (having had an engine and its landing gear ripped off before smashing back onto the runway, then skidding to a stop as it ground-looped) was burning so severely when the firefighters arrived, they decided to focus their efforts on the Pan Am plane.
All 248 crew and pax on KLM 4805 were killed.