One problem related to air bag has been reported for the 1998 Ford Expedition. The most recently reported issues are listed below.
Driving from va to mi, hit snow in OH. Hit patch of 'black ice', spun out, hit tractor trailer that was on the rights side of us with the front of my truck(1998 Ford Expedition), rolled 3-4 times. Slide about 20 feet. No airbag deployed through all of this.