Observed in western sky @ about 100 ft. flying to the south at about 10 to25 mph Flying in formation as geese would fly

We lived on the south side of Tucson about 1 mile from the Papago indian reservation.I went outside to feed our pigeons at about 7:00am before I went to school. I saw them to the west flying in formation like geese fly. They were about 100 ft. above the ground flying at about 10 to25 mph. I was very excited and started yelling for my mother and brothers. 2 of my brothers and mom came outside as we saw them move to the south. They were triangler shaped with rounded edges, grey in color, and seemed to be about 30 ft. or so. They proceeded towards the reservation slowly until they came to a small mountain where the reservation hospital is located. Behind the mountain is the Santa Cruz River which is dry most of the year. This is about 3 mi. from our home. They then stopped and hovered for a bit, then dissapered behind the mountain into I belive the Santa Cruz. After school that day my 2 brothers and I went to see if we could find any traces but didn't find any. That was 34 years ago and is just as vivid as then.