Resolution advisory (RA)

Resolution advisory (RA) – A warning issued by the Traffic Collision Avoidance System (TCAS) indicating an immediate threat of collision with another aircraft. This warning takes the form of a command to perform a vertical avoidance maneuver (e.g., Climb! Climb! ) These commands are products of TCAS II equipment. These commands take precedence over ATC instructions, but must be reported to ATC immediately upon receipt and execution.