Tapes of conversations between air traffic controllers and pilots waiting to take off from the Denver airport show that it was snowing so heavily just before Continental Air Lines Flight 1713 crashed that controllers could not see the planes as they taxied to the runway.
A transcript of an 85-minute segment of conversation, released yesterday by the Federal Aviation Administration, shows that controllers at the Denver tower were handling 42 flights just before and after the crash, and that they asked several pilots to clarify which plane was which.
Flight 1713 flipped and broke apart Nov. 15 as it was taking off from Denver's Stapleton International Airport, killing 28 and injuring 54 on board.
The tape shows that Flight 1713 stood in the snowstorm for 23 minutes after leaving the airline's de-icing pad before controllers cleared it for takeoff. Investigators at the National Transportation Safety Board are probing the possibility that the jet, an older-model DC9, may have stood long enough in the storm for ice to form again on its wings.
The safety board is expected to hold a hearing on the crash in Denver in February, although no date has been set.
The tape also confirms earlier reports of unusual maneuvers involving Flight 1713 before it took off, but provides no new leads. The pilots contacted the tower for the first time at 12:02 p.m., but did not ask for clearance from the gate. About 48 minutes later, the pilots contacted controllers to ask for clearance from the airline's de-icing pad to the runway.
The controller misunderstood the pilot's request to depart from the de-icing pad, and instructed the plane to proceed to the de-icing pad. The pilots missed the wording of the instruction and proceeded instead to the runway. The mistake left Flight 1713 at the end of the runway, while a Continental plane that had been behind it at the de-icing pad was cleared to take off first.
The mixup added two minutes to Flight 1713's wait at the end of the runway. Except for mentioning "we've got a little standoff goin' here, say again you do want us behind the Airbus," the pilots of Flight 1713 did not talk to the tower again until they were told at 2:12 p.m. to taxi into position at the end of Runway 35 Left.
The pilots acknowledged the clearance just after 2:14 p.m.
Eleven seconds later, controllers received the call: "Tower. Somebody just crashed on 35 Left. Big fireball."
Thirty-three seconds after that, the controller called, "Continental 1713." There was no answer.
In the remaining several minutes of the tape, controllers advised the pilots of planes in line at the end of Runway 35 Left that "we got a plane down with fire" and sent the planes back to the gate.