In this issue of ACAS II Bulletin we will look into events involving business jets. Their operations are often quite different from airline operations. Bizjets frequently operate outside controlled airspace which increases the risk of getting involved in an encounter with another aircraft, often general aviation or military. Also, they fly regularly to smaller airports, with limited or no ATC services. Consequently they can experience RAs at lower altitudes where alerts are generated with relatively short warning times, as illustrated by Events 1, 2, and 3. High climb and descent performance of many business jets make them more susceptible to receiving RAs due to high vertical speeds in some cases (Event 4). Even when the vertical rates are reduced, as recommended by ICAO, RAs will be issued in some circumstances (Event 5). Not all business aviation aircraft are TCAS equipped as, due to their weight or the number of passenger seats, they fall outside the equipage mandate. Even unequipped, aircraft will benefit from the collision avoidance protection offered by TCAS II, if they encounter an equipped aircraft (Event 6), provided they operate an altitude reporting transponder.