The Polskie Linie Lotnicze LOT SA (LOT Polish Airlines SA) Boeing 767-300 series aircraft was on a scheduled IFR flight from Chicago (O'Hare) International Airport, IL (U.S.A.) (KORD) to Warsaw (Okecie) International Airport, Poland (EPWA). The aircraft was en-route when the flight crew reported severe turbulence vicinity of North Bay at approximately 0203Z. The aircraft lost 5,000 feet of altitude (dropping from FL330 down to FL280). The flight crew elected to divert back to Toronto (LBPIA) at 0215Z. The aircraft completed a fuel dump from 0225Z to 0248Z. At 0255Z, the flight crew requested and were given a hold vicinity of the Simcoe VOR at 10,000 feet. At 0248Z (sic), the flight crew advised that they were unable to maintain their altitude and the aircraft climbed through 10,600 feet. At the time, JZA7927 was at 11,000 feet and their flight crew reported receiving a TCAS alert and flew their aircraft in a climb to 12,000 feet. The LOT flight crew commenced their approach to runway 23 at 0302Z. The aircraft landed without incident on runway 23 at 0316Z with ARFF services on standby. Ops. impact -- unknown. Aircraft landed safely runway 23 at 0316 Zulu. Emergency equipment on standby
UPDATE Supplemental information received from T.S.B. Initial Notification [#A09O0117]: The Boeing 767-300 series aircraft (SP-LPA, operated as Polish Airlines flight number LOT2) departed Chicago, O'Hare destined for Warsaw, Poland. In the vicinity of North Bay, Ontario, while cruising at FL330, the aircraft experienced a sudden and uncommanded overspeed condition, stick shaker and illumination of left and right electronic engine control (EEC) caution lights. The aircraft descended to FL280 before the situation was resolved. The aircraft diverted to Toronto (LBPIA) and landed without further incident. The T.S.B. deployed investigators to the site. Note: the class of investigation is being assessed.