One problem related to air bag not deploy has been reported for the 1999 Ford Aerostar. The most recently reported issues are listed below.
It was a rainy evening about 6:30 pm, I was traveling down a street at about 25mph trying to keep my speed at that because of the decline coming to a stoplight which I realized a second too late was red instead of green, I tried to stop and couldn't because the road was too wet and hit an oncoming vehicle in the driver's side front fender. The oncoming force of that vehicle spun me around into that street and propelled me into a large pole headon smashing my front end into my windshield. Upon that impact, my face hit my steering wheel, lacerating my lower lip complete thickness down into my chin, chipped my left front toothand broke the cartlidge in my nose with considerable bruising and swelling, all due to the fact that my airbags did not deploy.