21st Century Aerospace Infrastructure Act of 2020 This bill directs the Department of Transportation (DOT) to establish a pilot program, through FY2023, to issue transportation infrastructure grants to operators of outer space launch sites for the construction, repair, or maintenance of infrastructure and facilities at such sites. A launch site means the location on Earth from which a launch takes place Grants issued to an operator may not exceed $2.5 million for a fiscal year. DOT may issue supplemental grants to operators in support of state, local, or private matching under specified conditions.