This advisory circular (AC) describes acceptable methods and guidelines for developing takeoff and initial climbout airport obstacle analyses and in-flight procedures to comply with the intent of the regulatory requirements of Title 14 of the Code of Federal Regulations (14 CFR) Part 121, §§ 121.177 and 121.189, Part 135, §§ 135.367, 135.379, and 135.398, and other associated one-engine-inoperative (OEI) requirements relating to turbine engine-powered airplanes operated under parts 121 and 135. The methods and guidelines presented in this AC are neither mandatory nor the only acceptable methods for ensuring compliance with the regulatory sections. Operators may use other methods, if those methods are shown to provide the necessary level of safety and are acceptable to the FAA. This AC need not serve as the sole basis for determining whether an obstacle analysis program meets the intent of the regulations. However, the methods and guidelines described in this AC have been derived from extensive FAA and industry experience and are considered acceptable to the FAA when appropriately used. This document is intended only to provide clarity to the public regarding existing requirements under the law or agency policies.