Airport Infrastructure Readiness Act of 2020 or the AIR Act of 2020 This bill directs the Department of Transportation (DOT) to apportion Airport Improvement Program funding for FY2022 and FY2023 to an airport sponsor based on the number of passenger boardings at such airport that would result in the highest apportioned amount during either calendar year 2018, calendar year 2019, or the full calendar year prior to the current fiscal year. Additionally, DOT shall not calculate a benefit-to-cost ratio with respect to an air traffic control tower participating in the Contract Tower Program on the basis of an annual aircraft traffic decrease in FY2020 and FY2021. Under the Contract Tower Program, air traffic control towers are staffed by employees of private companies rather than by Federal Aviation Administration (FAA) employees. The FAA is required to perform a benefit-cost analysis to determine eligibility for participation in the program.