As the KLM made its 180-degree turn at the end of the runway, it was about 5:05 p.m. (17.05) local time. The Dutch crew was inching closer to flying time restrictions. Captain van Zanten opened the jet’s throttles and prepared to take off even before he had received ATC (Air Traffic Control) clearance. His first officer, Klass Meurs, admonished the captain:
Wait a minute, we don’t have an ATC clearance.
Closing the throttles, the captain said:
No, I know that, go ahead, ask.
First Officer Meurs advised the TFN tower:
KLM 4805 is now ready for take-off and we are waiting for our ATC clearance.
At 17.05:53, the Tenerife tower advised KLM 4805:
KLM 4805, you are cleared to the papa beacon, climb to and maintain flight level nine zero. Right turn after take-off, proceed with heading zero four zero until intercepting the three three five radial from Las Palmas VOR.
Before the controller finished speaking, and before his first officer repeated the ATC instructions, Captain van Zanten said, "Yes," and slightly opened the thrust levers. The plane was still held back by its brakes. The engines began to stabilize.