The union representing American Airlines’ maintenance workers says outsourcing is partly to blame for the loose seats discovered on some of the carrier’s Boeing 757 aircraft. The Transport Workers Union (TWU) says it is investigating why the seats were not installed securely. But Robert Gless, TWU air transport division’s deputy director, says, “Much of the work related to seat installation on American Airlines’ aircraft has been done by an outside firm, Timco, rather than by maintenance personnel employed by the airline.” Timco did not respond to telephone calls. American says that it is investigating the matter and that the issue seems to rest with a certain model of seats and how they fit into the tracks. “The seats were installed by American maintenance and contract maintenance,” a spokeswoman for the airline says. “The issue does not seem to be tied to any one maintenance facility or work group.” But TWU counters that these issues could worsen if American outsources more of its maintenance.