That same Friday for instance, G.M. began to make phone calls to the owners of its cars that had potentially defective air bags.

When the repairs are made to the last of 6.7 million potentially defective switches, the Ford recall may be the second largest in United States history.

Ford Motor said it expected to replace potentially defective air-bag inflators in about 3,000 cars, not 133.

Ford had previously issued a recall order to fix 8.7 million 1988-92 cars with potentially defective switches.

The 44,000 helmets in use by service members were recalled by the U.S. Army in May 2010 due to potentially defective materials being used.

But late last week, the company said it would have enough parts in March to replace all potentially defective coils.

For Pam Alexson, the decision whether to have a potentially defective heart device removed and replaced was easy.

In addition, this problem is especially troublesome for Ford because the potentially defective 1991 Ford Explorer has been one of its few strong-selling vehicles.

At the time, Guidant executives were faced with the choice of recalling potentially defective heart defibrillators or allowing doctors to implant them.

Critics said the case was typical of the F.A.A.'s lack of urgency about cases involving potentially defective spare parts.