Takata Corp., the company whose faulty air bags are behind a record vehicle-safety recall, is depending on three of its key competitors to produce the majority of millions of replacement parts.

By March, Autoliv Inc., Daicel Corp. and ZF TRW Automotive will make about 68 percent of the inflators used to repair recalled vehicles, according to a letter sent by Takata to U.S. regulators. The three companies produced about 50 percent of the inflators for replacement kits in June, Takata said.

The disclosure was part of responses by automakers and air bag suppliers last month to questions by the National Highway Traffic Safety Administration on the progress of the safety recalls. More than 40 million vehicles have been recalled worldwide as a result of Takata air bag inflators that rupture during deployment, a defect linked to eight deaths and more than 130 injuries.