From the Background: "The United States and the EU have long claimed that the other either directly or indirectly subsidizes their domestic civil aircraft industry. According to the United States, the EU and the governments of certain EU member states-- France, Germany, Spain, and the United Kingdom (UK)-- have provided, over the years, subsidies to their respective Airbus-affiliated companies to aid in the development, production, and marketing of large commercial aircraft (e.g., through equity infusions, debt forgiveness, debt rollovers, marketing assistance, and alleged political and economic pressure on purchasing governments). The EU, on the other hand, claims that Boeing benefits from U.S. government support, mainly in the form of research and development funds from the National Aeronautics and Space Administration (NASA), the U.S. Department of Defense, and other agencies. Furthermore, the EU claims that Boeing receives subsidies in the form of tax reductions and exemptions, as well as infrastructure support to develop and produce new aircraft."
CRS In Focus, IF11364
Congressional Research Service: https://crsreports.congress.gov/