There have been some reports from recent years of people having interference with their cell phones during UFO encounters, ranging from being unable to get a cell phone signal to not being able to use a cell phone camera. For convinence, here's the categories of UFO sightings developed by the late Dr. J. Allen Hynek (first director of the Center for UFO Studies, and the former scientific consultant to Project Blue Book):
Nocturnal Light (NL): your typical light-in-the sky. Most can be readily explained (aircraft, meteors, other astronomical causes, lighted balloons, etc.), but about 10% have no explanation, due to the behavior of the light and/or the description of the light. Some of the sightings from the Belgian wave of 1990 are in this category, but others are in the R-V or CE-1.
Daylight Disc (DD): What most people think of when they hear the term "flying saucer." A structured object, often a disc, is seen in daylight hours. However, the category extends to any shaped object seen in daylight. (cigar, oval, egg, etc.) The Kenneth Arnold sighting from 24 June 1947, the 15 Aug 1950 Great Falls, MT film, or the Tremonton, UT film from 1952 are examples.
Radar-Visual (R-V): The most difficult to explain. A witness, either on the ground or in an aircraft, sees an object and there is radar confirmation via either ground or airborne radar. Examples of unexplained R-Vs include the famous Washington National sightings in 1952, the Lakenheath-Bentwaters Radar-Visuals in 1956, and the RB-47 case in 1957, and the famous Tehran jet chase from 1976.
Close Encounter of the First Kind (CE-1): A structured object is seen by the witness(es) at a distance of 500 ft. or less, but no other effects are noticed. An example of this would be the chase by three Ohio lawmen of a UFO for 85 miles from Ohio into Pennsylvania on 14 April 1966, at speeds exceeding 105 MPH, the "Incident at Exeter" (NH) on 3 Sep 1965, and many of the sightings from both the Hudson Valley (NY) wave from 1983-85, and the Belgian wave of 1990.
Close Encounter of the Second Kind (CE-2): A structured object is seen, and that object either leaves evidence behind, or otherwise interacts with its surroundings. (landing marks, interference with TV, radio, and with vehicle engines; also some physical effect on the witness-some have been burned, or suffered nausea, for example) Examples include the Val Johnson encounter in Minnesota in 1979 (the witness suffered damage to his sheriff's dept. patrol car, and a mild case of "welder's burns" to his eyes), and the 1980 Cash-Landrum encounter outside Houston in December, 1980, and a famous landing at Trens-en-Provence, France in 1981.
Close Encounter of the Third Kind (CE-3): Besides the object, entities are observed. This category does not include reported abductions. The entities are often seen outside the craft or going inside/outside. Some reports do not involve landings, but the occupants are seen thru domes or windows on the craft. The famous Soccoro (NM) landing on 24 Apr 1964, and the Kelly-Hopkinsville encounter on 21-22 Aug 1955 are examples.
Close Encounter of the Fourth Kind (CE-4): Abduction of the witness. Sometimes the abductions occur only once (the famous Betty and Barney Hill case from 1961, or the Travis Walton case from 1975), or the person is abducted on a number of occasions (see Budd Hopkins' book Intruders) .