The agreed terms and definitions and the operational use of the combinations of the terms listed in Annex A are based on: a. The two aspects of tactical control of aircraft@ namely the aircraft's mission and the aircraft's safety. b. The fact that@ notwithstanding the safety aspects covered by the set of standard aircraft tactical control terms@ the aircraft commander is ultimately responsible for the aircraft's safety. However@ this ultimate responsibility of the aircraft's commander does not relieve the controlling unit from taking any conceivable measure within the range of possibilities to ensure the aircraft's safety. c. The fact that close and loose control will normally be associated with the terms positive and advisory@ however@ in exceptional circumstances the terms close@ loose@ positive and advisory may be used in isolation. In this situation only the definition associated with the single term in use describes the control being offered by the controller. d. The premise that no further prowords or codewords additional to the operational combinations listed in Annex A are required to tactically control aircraft.