Sixty years of stonewalling by the American government about unidentified flying objects had caused people to eventually forget the subject. Still, the story would not totally die, due to the repeated sightings.
In the case of the gigantic flat "thing" hovering less than a thousand feet over north Texas, the cover story offered by the government was laughable. After denying that there had been aircraft near the sighting area, southwest of Dallas, they later said that there had been ten F-16's in the area. Those who had seen the odd vehicle when it was hovering and then had shot off out of sight, they knew very well that it had not been F-16's. They knew what the F-16's were like and had seen then later flying after the large vehicle.
The generalized cover story was that whatever was seen could always be explained as something totally natural and usual. That served to cover both the alien craft and crashes and the prototypes from the various black projects that used technology developed from the alien crash sites.