This solicitation requests proposals for Phase I of the AACES 2050 Advanced Aircraft Concepts for Environmental Sustainability program. The National Aeronautics and Space Administration Glenn Research Center seeks concepts and technologies to reduce aircraft environmental impact by 2050 through lower emissions, noise reduction, and increased energy efficiency. Offerors should propose innovative early-stage research projects lasting up to 6 months. Proposals are due by February 28, 2023 and awards will be made by May 2023. Projects should aim to advance aircraft configurations and propulsion technologies to meet aggressive environmental targets.