Fran Ridge:
Afternoon. An F-82 fighter was dispatched from Moses Lake AFB, near Hanford, Washington, to intercept a flying disc that was observed hovering in restricted air space over the Hanford Atomic Plant at an altitude of 17,000 to 20,000 feet.  The silvery, disc-shaped object bad been visually sighted by crew and personnel from the Hanford radar station and confirmed on radar.

Dr. J. Allen Hynek:
A call quickly went from the Hanford station to Moses Lake AFB but before the F-82 was airborne the disc suddenly took off in a southerly direction at a speed greater than that of a jet fighter!  The Air Intelligence Information Report on this case states that the pilot of the F-82 was instructed to search for the object and "intercept it in hopes that it might be a disk."  However, the object had sped out of the range of ground radar and the pilot of the F-82 was not able to locate it.  A short time later, another aircraft was observed on radar in the restricted air space of the Hanford Atomic Plant.  This one was positively "identified" as a commercial aircraft dropping leaflets announcing a rodeo! Yes, you guessed it.  Blue Book files carry this UFO sighting under the classification of "aircraft," based on the assumption that the commercial aircraft and the UFO were one and the same object.  This, despite the following comment by the investigating officer: It is believed that two separate and distinct alert conditions existed on the afternoon of 21 May 1949.  The first was caused by the sightings of Flying Saucers (noted) by Hanford using a telescope and the operations crew of the 637th ADCC.  The second was caused by the  dropping of leaflets by an aircraft into the Hanford area.  It is believed that there is no connection between the two events.

Detailed reports and documents
docs/490521hanford_docs.htm (Dan Wilson)