This legislation, known as the Aviation Funding Stability Act of 2025, aims to prevent disruptions to Federal Aviation Administration (FAA) operations during a government shutdown. It establishes a mechanism to ensure that the FAA can continue its critical programs, projects, and activities even if a regular appropriation measure or continuing resolution is not enacted by the start of a fiscal year. Specifically, the bill authorizes the use of funds from the Airport and Airway Trust Fund for various FAA accounts, including Operations, Facilities and Equipment, Research, Engineering, and Development, and Grants-in-Aid for Airports. These funds would be available at a rate not exceeding the previous fiscal year's funding levels and would cover the period from the first day of a lapse in appropriations until either a new appropriation becomes law or 30 days have passed, whichever occurs first. The bill also amends the Internal Revenue Code to facilitate these expenditures, ensuring stability for essential aviation functions.