Expanding Regional Airports Act This bill directs the Department of Transportation (DOT) to establish a grant program for general aviation and nonprimary commercial service airports to improve passenger and flight capacity. Grants may be used for (1) activities that improve passenger and flight capacity at the airport, including the expansion of passenger and property screening facilities, runway lengthening, hangar construction, and improving passenger facilities; and (2) costs incurred to comply with certain operational and security requirements. DOT must provide 3 to 10 grants per fiscal year to eligible airports (i.e., general aviation or nonprimary commercial service airports that serve a community with a population of at least 75,000).