Methods that might be considered for in-flight thrust determination (IFTD) and uncertainty analysis for turbofan engines are presented. From four IFTD methods presented here, three are standard in the aircraft industry and are documented in SAE AIR 1703, and the Residual Error Method; the fourth method is the author's alternative proposal. The document includes also full uncertainty analysis assessment as per SAE AIR 1678 . This document is intended also to provide appropriate background information to gain a perspective of the major aspects and processes that might be used for the determination of in-flight thrust and its uncertainty. An application to a specific program is presented, which is a case study that illustrates the practices and results for determination of in-flight thrust for a modern turbofan engine.