DALLAS (AP) - The federal pension-insurance agency is increasingpressure on American Airlines to save its retirement plans insteadof dumping its pension obligations. The Pension Benefit Guaranty Corp. said Tuesday it filed lienstotaling $91 million against some assets of the airline's parentcompany, AMR Corp., which filed for bankruptcy protection inNovember. Last week, AMR paid only $6.5 million of a scheduled payment ofnearly $100 million for its pension plans. AMR and its lawyers have raised the possibility that the companymight freeze or terminate retirement plans that cover about 130,000employees and retirees. The company could make its intentions clearon Wednesday, when it presents new contract proposals to itsunions.