WASHINGTON, April 30 (Reuters) - The U.S. Federal Aviation Administration on Tuesday said it was seeking a $247,500 civil penalty against American Airlines for sending an unmarked, hazardous oxygen generator aboard a Federal Express plane. American Airlines, a unit of AMR Corp. (AMR), offered the oxygen generator to Federal Express (FDX) on Aug. 21, 2001, for transport from New York City's John F. Kennedy International Airport to American's maintenance and engineering center in Tulsa, Oklahoma, the FAA said. AMR is based in Fort Worth, Texas. A chemical oxygen generator is considered to be hazardous material by the FAA. "The package containing the generator was not properly classed, described, packed, marked, labeled and in condition for shipment when it was offered to Federal Express," the FAA said, adding that American personnel in Tulsa discovered the violation. An American Airlines spokesman was not immediately available for comment. The airline has 30 days to respond upon receipt of the enforcement letter. A shipment of oxygen generators was blamed for the fiery crash of a ValuJet Airlines DC-9 jet into the Florida Everglades in 1996, killing 110 people aboard. Shares of AMR fell 27 cents to close at $21.47 on the New York Stock Exchange.