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30 March 2010

NTSB to investigate near miss involving a 777 over San Francisco

United Airlines 777 N216UAThe NTSB has launched an investigation into a nearly catastrophic collision between a United 777 and a small private aircraft over San Francisco last weekend. The NTSB estimates that the two aircraft missed each other by less than 300 feet.

At about 11:15 a.m. PDT on March 27, United Airlines Flight 889, a B777-222 (N216UA) carrying 251 passengers and 17 crew members on a flight to Beijing, China, had just departed from San Francisco International and was climbing through about 1,100 feet when both air traffic control and the aircraft's collision avoidance system reported air traffic nearby.

Example of an AeroncaThe flight crew saw a small aircraft, an Aeronca 11AC (N9270E), in a hard left turn traveling from their 1 o'clock to 3 o'clock position. The first officer interrupted the climb and leveled out the aircraft. Both crew members reported seeing only the underside of the Aeronca as it passed to within an estimated 200-300 feet of the 777.

After the encounter, the flight crew continued to Beijing without further incident.

You can listen to this edited recording of transmissions among air traffic controllers and the two involved aircraft (Source:

Midair collisions that result in passenger deaths on large jet airliners are very rare events. According to's list of midair collisions, the last midair involving a jet airliner was a 29 September 2006 collision between a Gol Linhas Aereas 737-800 and ERJ135 Legacy 600 executive jet over Brazil. All on board the 737 were killed, and everyone on the ERJ135 survived.

The last airliner midair in the US was a 31 August 1986 collision between an Aeromexico DC9-32 and a Piper Archer over Cerritos, CA. All occupants of both aircraft were killed. More recently, a private plane and a sightseeing helicopter collided over the Hudson River near New York, killing all on board both aircraft.

Photo credits: Drewski2112 (777), Wikipedia (Aeronca)


  1. The following set of comments was seen on the JetCareers forum at

    It's apparent that the Aeronca pilot was on a valid Class B clearance transitioning north to south at 1500 ft (Hwy 280 transition?). I've heard that with this transition SFO tower often reroutes VFR aircraft to overfly midfield if they have straight out departures from rwys 28L/R to protect their climb (between Montara Mountain and San Bruno Mountain, an area known as "the Gap").

    In this case, the Aeronca (N9270E) was given a traffic advisory of the departing B777 while it was still at 500 ft, reported it in sight and was issued visual separation instructions to pass BEHIND the departing aircraft, which they read back. Given the fact that the UAL pilot and tower blocked each other it sounds like the flight crew was already responding to their TCAS Resolution Advisory and querying ATC by the time they got the traffic advisory from tower. The aftermath is pretty wild, I can only imagine what they asked SFO tower on the discreet frequency they got...

    I don't mean to speculate too much while the NTSB does their thing. However, I live just north of San Francisco and have been wanting to make a similar flight as the offending aircraft down Ocean Beach to Half Moon Bay, and am a little spooked by the whole thing now.

    Other than complying with the instructions you read back to ATC, what else if anything do you guys think can be learned from this?

  2. Dr. Curtis:
    One factor in this case could be airspace clasification and the VFR operation mantaining his own separation i mean the Aeronca 11AC .

  3. Im an retired Radar ATC, some times the ATCS abuse of the concept of "mantain your own separation" on VFR condition, I bealive to avoid mixed operation in congested airspace is a good mitigation practice