This analysis of the US large commercial aircraft (LCA) manufacturing sector addresses the question of how the US subsidizes this area of the industry. The information provided here is intended to back up the LCA trade debate, as since the beginning of the 1990s, the US government has felt able to increase federal support for the large commercial aircraft sector, seemingly without fear of invoking a legal challenge under the ensemble of GATT regulations, which apply to LCA trade. The analysis in this text aims to contest this assumption and show that subsidy does indeed exist and the study seeks to show how the US LCA manufacturing sector benefits from the research and development funded by the American federal government.