What happened
A Beech 99 departed on a VFR flight and began a climb to 10,500 feet on a heading of 175 degrees. Upon reaching 7,000 feet at the boundary of Class B airspace, the TRACON controller terminated radar service for the aircraft.
Forty seconds later, the crew of a Boeing 737 contacted TRACON while on the Cresso 3 Arrival (STAR). The controllers cleared the Boeing 737 to descend to 10,000 feet on a converging vector of 020 degrees. Fifty seconds after this clearance, TRACON advised the Boeing 737 crew of traffic—the Beech 99—located three miles ahead in the opposite direction and 1,700 feet lower. The controller did not issue a safety alert or mention that the Beech 99 was climbing. Eighteen seconds later, TRACON informed the Boeing 737 pilots they could "climb as you wish."
The first officer, who was flying the TCAS-equipped Boeing 737, responded to a resolution advisory by using the autopilot but failed to press the "level change" button, which caused a delay in the avoidance maneuver. The Boeing 737 crew observed the Beech 99 at close range, and the first officer performed an abrupt maneuver to avoid a collision. During this maneuver, one flight attendant was injured. The pilot of the Beech 99 observed the Boeing 737 behind a window post but was unable to take evasive action. The aircraft passed each other with an estimated vertical separation of 200 feet and no lateral separation.
Findings
An analysis of the TCAS event concluded that had the Boeing 737 pilots responded to the TCAS advisories within the system's design parameters, there would have been 700 feet of vertical separation without the need for abrupt maneuvering. The Cresso 3 STAR is a heavily traveled area frequently used by pilots of small VFR aircraft.