Ray Fowler:
Another civilian representative assigned to Grand Forks AFB, North Dakota, told me that an Air Force major friend of his got a good close look at a completely unconventional craft maneuvering in the area between the air base and missile site. As he got out of his car and approached it, it took off at tremendous speed. Superiors ordered him not to talk about the incident. 

On March 5, 1967, just 15 days prior to the Malmstrom AFB incident, the 91St Strategic Missile Wing at a sister base also had an unwelcome visitor. Aerospace Defense Command radar tracked an unknown target descending over the Minuteman missile installations at Minot AFB, North Dakota. Strike teams were alerted and sighted a metallic disc- shaped craft ringed with bright flashing lights moving slowly over the supersensitive area.

Three armed teams in fast trucks pursued the alien vehicle as it maneuvered and finally stopped and hovered 500 feet off the ground. The strike teams held their fire. They had orders to capture it undamaged if it should land. Then abruptly it began moving once again and circling directly over a launch control facility. Back at Minot, F-106 fighter planes were awaiting orders from the North American Air Defense Command to launch an attack. Base operations became impatient and had just decided to scramble the jets without confirmation. Suddenly the UFO climbed straight up and streaked away at incredible speed.

A civilian employee at Malmstrom told me a bright, round, white object circled the missile site for prolonged periods on April 10 and 11, 1967. Apparendy its altitude was beyond the operational capabilities of Air Force interceptors. Personnel who had sighted the strange object were told that it was a highly secret government test vehicle and not to be discussed. The local radio station was told to keep quiet about it

Source: Casebook of A UFO Investigator, page 187 - Ray Fowler