The third edition of Air and Gas Drilling Manual describes the basic simulation models for drilling deep wells with air or gas drilling fluids, gasified two-phase drilling fluids, and stable foam drilling fluids. The models are the basis for the development of a systematic method for planning under balanced deep well drilling operations and for monitoring the a drilling operation as well construction project advances. Air and Gas Drilling Manual discusses both the oil and natural gas industry applications, and geotechnical (water well, environmental, mining) industry applications. Important well construction and completions issues are discussed for all applications. The engineering analyses techniques are used to develop pre-operations planning methods, trouble-shooting operations monitoring techniques and overall operations risk analysis.