2007 Lincoln MKX air bags problems

The contact owns a 2007 LINCOLN MKX. The contacts husband stated while driving approximately 35mph when the driver side airbag inflated without warning which resulted in the contact's husband to lose control and crash the vehicle into a vehicle in front. 4 persons were injured (the contacts husband and 3 other individuals that were in the other vehicle) the occupants in the other vehicle went and sought medical treatment (contact does not know the type of injuries) while the contact's husband did not seek medical…

I received a letter from the lincoln motor company in july 2016 informing me of the safety recall for my vehicle regarding the passenger frontal airbag. I have called my local lincoln service department four times over the past year and a half to have the problem corrected, and each time I've been told that parts are not yet available. If there is a known hazard, shouldn't the problem be remedied quickly? I've now waited 16 months and the problem is still not corrected.