On 29 August, a mid-air collision above Southern Kenya was narrowly avoided thanks to a TCAS alert (*) and the alertness of the pilots. Both an Ethiopian Airlines Boeing 737 (ET-ASJ) and a Neos Boeing 767-300 (I-NDOF) were flying at the same altitude of 37,000 feet. While the 737 was operating flight ET858 between Johannesburg and Addis Ababa, the 767 was operating a flight from Verona to Zanzibar as NOS252.
Less than 1 minute before both flight paths converged, the Ethiopian Boeing 737 climbed to 38,000 feet and thus avoided a potential conflict. One minute later the aircraft descended again to its cruising altitude, both flights continued to their destinations without further incident.
(*) Wikipedia TCAS: A traffic collision avoidance system or traffic alert and collision avoidance system (both abbreviated as TCAS, and pronounced /tiːkæs/ “tee-kas”) is an aircraft collision avoidance system designed to reduce the incidence of mid-air collisions between aircraft. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder, independent of air traffic control, and warns pilots of the presence of other transponder-equipped aircraft which may present a threat of mid-air collision (MAC). It is a type of airborne collision avoidance system mandated by the International Civil Aviation Organization to be fitted to all aircraft with a maximum take-off mass (MTOM) of over 5,700 kg (12,600 lb) or authorized to carry more than 19 passengers. CFR 14, Ch I, part 135 requires that TCAS I be installed for aircraft with 10-30 passengers and TCAS II for aircraft with more than 30 passengers.
ACAS / TCAS is based on secondary surveillance radar (SSR) transponder signals, but operates independently of ground-based equipment to provide advice to the pilot on potential conflicting aircraft.
2018-08-29: Serious Airprox incident at night over southern Kenya between NEOS flight #NOS252 (B767-300, I-NDOF) from Verona to Zanzibar and Ethiopian AL #ET858 (B737, ET-ASJ) from Jo’burg to Addis. Both aircraft were at 37,000 ft. pic.twitter.com/CL3fiW3lMQ
— JACDEC (@JacdecNew) September 5, 2018