On the scope, ring angels produce outwardly expanding rings and arcs that sometimes move on and off the screen at incredible speeds. Such echoes have been a fairly common phenomenon in England since 1940 and 1941[VIII-15], and experimental research has shown that many of those occurring at dawn or at dusk are caused by flocks of starlings. At dawn thousands of starlings leave the roost in waves at intervals of about half a minute. The birds in each wave are often closely packed in a tight circle or semicircle as the wave ascends. All are flying outward, dispersing in all directions, so that the ring diffuses rapidly on the radar screen and disappears, but is followed almost at once by a new ring. At dusk the birds may return separately to the roost during the course of an hour. Sometimes, however, they assemble first in a field some distance from the roost; they finally take off at the same time as a group and head for the roost in a single giant wave, causing a tremendously impressive but quickly vanishing angel on the radarscope. Ring echoes observed at Texarkana, Arkansas, have been traced to the movements of red-winged blackbirds. Thousands of birds flying out from a common roosting ground a few minutes before sunrise show up on the PPI scope as an expanding ring that grows broader and more diffuse with time until the composite echo breaks into individual ones and fades at a distance of twelve to thirty-five miles[VIII-16]. Other types of ring angels have been observed on radarscopes, but the causes are not yet fully understood[VIII-17, VIII-18]. Recognizing the true character of these radar angels and spurious reflections has tremendous importance for the security of the United States. Our Early Warning System, designed to notify Air Defense of imminent attacks by intercontinental ballistic missiles, has already had troubles with such radar ghosts. On October 5, 1960, a signal from Thule, Greenland, to the North American Air Defense Command flashed the warning, “Massive ICBM attack is underway.” The Canadian officer in charge had only seventeen minutes in which to decide whether to order several hundred bombers of the Strategic Air Command to retaliate against the USSR or to push the button that would cause our long-range missiles with atomic warheads to come roaring out of their underground sites. He immediately asked Washington: Where was Khrushchev? Khrushchev was in New York at the United Nations: the officer did not push the button that would have set the world at war. Later, he learned that radar beams reflected from the moon had produced the terrifying angels. This incident is only one of the reasons why the Air Force continues to be interested in radar UFOs. Failure to identify them correctly could threaten the effectiveness of our patrol system. _The Rapid City Sighting_