It was around the middle of april of 1972. it was broad daylight, around 1100 hours. we were on our way back to base at malmstrom afb, montana and was a beautiful crisp spring day. the sun was shining and the sky was clear blue and nice white clouds all around. i was the security police officer on duty, responsible for protection of the targeting team and codes. i was with the targeting team which consisted of 1 capt., 1 lt., and the driver(tsgt), and 1 ssgt and sgt. we were approximately 30 miles from base when suddenly, the vehicle engine died. we pulled over and checked the engine. the capt tried to use the radio to call wing security to inform them what had happened, but got no squelch or answer. he asked me to call my central security control for assistance. but i also could not get any response. we decided to exit the vehicle and stretch our legs. as i looked up, i first saw a strange cloud formation in the sky...Then, in a few seconds. i saw what appeared to be a craft of some kind. silvery. with a squared front and very large...Very very large coming from the cloud. it was hovering and turning very slowly from the cloud. all of us were seeing this object now; yet, none of us could talk; just stare. it was in a position approximately 45 degrees from us, at a height of approx. 400-500 feet. the craft itself was about the length of 4-5 football fields! it's height was about 300 ft. we were stunned to see the immense size of the object; yet not scared, just in awe! the craft just hovered as if observing us. about 10 minutes later, the craft stared turning toward the south, began to pitch upwards and in an instant; was gone. the captain asked if everyone was alright; to which we acknowledged yes. he then asked if we had all seen the craft. to which we said yes. suddenly, my radio squelched and i asked to captain if i could inform my superiors. he said no. that we should wait until we return to base and he would make the report. the tsgt who was driving tried to start the vehicle and once he turned the key, the engine came back to life. upon our arrival at base, we immediately went to key and codes so that the capt. and lt. could debrief and report. he ordered us to stay in the vehicle until he returned. upon his return, his face seemed white as snow. he told us that if we value our careers; that we never reveal or report what we saw to anyone....Ever. at the time of that event; i was a very young airman with a top secret clearance. i knew what he was saying. i am now 65 years old and am not bound by secrecy. i know what i saw. i still look at the sky and the clouds. there isn't a day that goes by i don't. i am hoping that the others who were with me that day, report this too. someone needs to know, we are not alone... i don't know where this craft came from, whether from outer space, or from another dimension or time...But i know it was real.