Tenerife: Deadliest Air Accident

While First Officer Meurs repeated the ATC instructions, van Zanten released the brakes at 17.06:11. One second later, he said

Let’s go, check thrust.

The First Officer continued to read back the ATC clearance to the tower. He finished his communication with these words:

We are now at take-off.

Listening in, the Pan Am pilots became concerned. Didn’t the KLM crew know both planes were now facing each other on the mist-shrouded runway?!

After the KLM first officer repeated the ATC clearance, and at the precise moment the tower replied by telling the KLM crew,

...stand-by for take-off, I will call you.

Clipper 1736 advised the tower

...we are still taxiing down the runway, the Clipper 1736.

KLM 4805 heard neither ground control nor Pan Am’s first officer. (Follow the link to 1706:19.39) The simultaneous transmissions sounded like a three-second squelch to the KLM crew.

Another exchange between the tower and Pan Am 1736 was heard by KLM’s flight engineer:

Tower: Roger, papa alpha 1736, report the runway clear.

Pan Am 1736: OK, we'll report when we're clear.

At 1706:34.7, KLM’s Flight Engineer William Schreuder became alarmed (scroll to the end and look for the transmission at 1706:34.7):

Is he not clear, that Pan American?

Both the captain and first officer replied simultaneously:

Yes.

They were wrong.

KLM 4805 continued to roll down the runway on a collision course with Pan Am 1736.