Incident at Thunder Bay, Ontario (ATS operating irregularity)


1996-05-31: Attempting to assist the aircraft involved to find a smoother ride, the controller cleared NWA55 (B747), ACA126 (EA32), and CDN968 (EA32) down to FL290. He failed to recognize that the underlying sector's cap had been raised to FL330 and therefore the descending aircraft came into potential conflict with CDN954 (B737) and NWA17 (B747). Shortly after issuing the descent clearance the controller recognized the error and took immediate steps to correct the situation. Although separation between the involved aircraft was never actually less than the required minima, the initial descent clearances did not ensure that separation would be maintained. The occurrence is being investigated by local management.


CADORS Number 1996C0171
Occurrence Type Incident
Reported By
Occurred At 1996-05-31 - 20:40
Day or Night? Day-time
Fatalities 0
Injuries 0
Aerodrome ID
Aerodrome Name
Geographic Location Ontario, Canada, North America, Ontario Region, Thunder Bay, Ontario
TSB Occurrence Number
TSB Class of Investigation
AOR Number
Reported By
Categories ATM/CNS
Events ATS operating irregularity

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