The NTSB release says:
At about 11:15 a.m. PDT on March 27, the crew of United Airlines Flight 889, a B777-222 (N216UA) destined for Beijing, China, carrying 251 passengers and a crew of 17,The next time someone tells you that commercial airline pilots are glorified bus drivers, remind them of this scenario.
was cleared to takeoff from San Francisco International Airport (SFO) on runway 28L and climb to an initial altitude of 3,000 feet. The first officer, who was flying the aircraft, reported that after the landing gear was retracted and the jet was at an altitude of about 1,100 feet, the tower controller reported traffic at his 1 o'clock position.
Immediately following the controller's advisory, the airplane's traffic collision avoidance system (TCAS) issued an audible alert of "TRAFFIC TRAFFIC." The pilots saw a light high wing airplane, an Aeronca 11AC (N9270E), in a hard left turn traveling from their 1 o'clock to 3 o'clock position. The first officer pushed the control column forward to level the airplane. Both crew members reported seeing only the underside of the Aeronca as it
passed to within an estimated 200-300 feet of the 777.
TCAS then issued an "ADJUST VERTICAL SPEED" alert, followed by a "DESCEND, DESCEND" alert. The first officer complied and the flight continued to Beijing without further incident.
Given the estimated speed of both aircraft, disaster was literally just one second away.
It recalls one of the most tragic air disasters in the country, when a small plane collided with a jetliner over San Diego many years ago.
What happened? Almost certainly this will come down on the small airplane pilot and an air traffic controller. No airplane is allowed within about 5 miles of an airport like San Francisco (and also Minneapolis-St. Paul, where the no-fly zone extends to the ground near the High Bridge in St. Paul) unless they've been given clearance to enter and are under the guidance of a controller.
I've found the actual tape of the incident. In this tape, the tower controller in San Francisco clears the United flight for takeoff and tells the smaller plane to be looking for traffic. The smaller plane reports he has the Boeing 777 in site, and he is told to pass behind the jet. The controller then tells the pilot of the 777 that the small plane is "no factor."
She's not happy.
"That set off the TCAS," she says, which is the collision warning system.