WASHINGTON — The TSA is considering ending screening of passengers at smaller airports across the country to focus security efforts at the largest airports. It is unclear how advanced the proposal is and whether it will ever be adopted. Still, aviation-security experts reacted with alarm, saying it could make flights at smaller airports inviting targets for terrorists. CNN reported Wednesday that the Transportation Security Administration is considering whether to end passenger screening at airports that serve planes with 60 seats or fewer. The report cited senior agency officials and internal documents. In a statement, the TSA said no decision has been made. Security experts say that while passengers on the largest jets would still be screened, terrorists could target regional planes at small airports. Those flights still carry dozens of passengers.