(MONEY Magazine) – Airlines have been weaning fliers off paper tickets since the introduction of electronic ones in the late '90s. Now they're pushing harder, with both new penalties and incentives. This spring, Delta joined American and Continental in charging $10 extra for a paper ticket on most flights. Northwest and U.S. Airways are considering a similar fee. At the same time, major airlines are making it easier for travelers to use e-tickets. One advantage paper tickets have had is that they're transferable, a plus if your flight is canceled. This year, airlines have started linking their computer systems to let you electronically switch to a flight on another carrier. The latest digital step for travelers is printing boarding passes from an airport kiosk, which earns you miles with some airlines. Check yourself in at American and you'll get 500 bonus miles. --M.J.