floating disc, numerous quick course changes, shortly afterwards aircraft seeming to "grid" search area.

Approx. 1971/1974 early eve.6 - 7 pm & towards the end of summer.  
Myself, sister & friend, were playing.  As we exhausted ourselves with summer play, knowing in a very short time our mothers would call us in for the night.  We lay on the front lawn giggling, and staring at the early evening sky.  
We then noticed a large, typical disc shaped object, silvery in color.  It made unusual movements, floated near and far within seconds, then would suddenly fly off into a direction, stop hover, and again change altitudes and direction like I have never seen since.   
Within minutes several Air Force jets (?) along with a couple helicopters appeared which seemed to fly in a searching grid type pattern.   Just prior to them showing up the disc moved westward toward the mountains.  
I've never spoken of this & would like to research further, I.E.  A more precise timeframe, newspaper articles, and or sightings by others, along with any cooberating info. 
I know what I saw, I'm a professional, owning a business for 15 yrs.  
This has haunted me for years.
Witness indicates that the date of the event is approximate.  PD