LONDON, Dec. 30--Two members of a Royal Air Force bomber crew in World War II believe they can explain one of the unsolved mysteries of the war: the disappearance of the band leader Glenn Miller. The two say they fear the band leader's plane was downed over the English Channel by bombs jettisoned from their own plane as they returned from an aborted mission.
    The two -- the navigator and the pilot -- said their four-engine Lancaster bomber was one of some 150 returning from an aborted mission on Dec. 15, 1944 -- the same day Mr. Miller took off in bad weather from an airfield near Bedford, England, on a flight to Paris, where he was to give a Christmas show. The two R.A.F. crewmen said that after the jettisoned bombs exploded, they saw a Norseman aircraft fall into the sea below them, apparently knocked out of the sky by shock waves [from the exploding bombs]. The plane carrying Mr. Miller, who was then a Major in the Army and leader of the Army Air Force band, was a Norseman D-64. [Norseman aircraft were rarely seen in Europe during World War II.]
    The official version of the band leader's disappearance is that his aircraft vanished in the channel fog, perhaps disabled by ice on its wings. Other theories were more bizarre: that he faked his own death, that he was a secret agent, that he died in a Paris brothel with the crash story as a cover-up, or that he was the victim of black marketers.
    The R.A.F. crew's story was originally raised in public last year by the navigator, Fred Shaw, who now lives in South Africa. His theory, which appeared in South African newspapers, was discounted, however, by members of the Glenn Miller Appreciation Society, a London group with an abiding interest in Mr. Miller's life and music, on the grounds that no R.A.F. planes were assumed to be in the air that day because of the poor weather.
    But one member of the society, Alan Ross, of Liverpool, England, investigated Mr. Shaw's claims. Mr. Ross wrote to the Defense Ministry and placed an advertisement in the R.A.F. Association Journal, 'Air Mail', seeking other members of the Lancaster's crew.
    Mr. Ross said that members of the Appreciation Society believed the Defense Ministry had been asked about the matter years ago and that the ministry had replied that "not even the pigeons were flying that day." Defense Ministry officials, however, could not recall such a query.
    Records found at the Ministry of Defense by E. A. Munday, of the Air Historical Branch, confirmed that a squadron of Lancasters had, in fact, taken off at noon on Dec. 15, 1944, and had flown on a course over northern France, near the Belgian border, on a mission to attack the railway yards at Stegen, Germany.
    "Before entering German-controlled airspace, the force was recalled," Mr. Munday said. "According to standing orders, the bombs were jettisoned in designated areas before landing."
    In a letter last May, Mr. Munday wrote Mr. Shaw: "Until your story appeared in the South African press in 1984, the R.A.F. had always regarded Miller's death as a strictly U.S.A.A.F. matter, as the result of some sort of flying accident, probably as a result of poor weather conditions. We have received letters at various times asking about it, some of which put forth theories, some feasible, and some not so feasible.
    "Up until 1984, the only R.A.F. connection was that Miller's plane had taken off from the R.A.F. airfield at Twinwood Farms, Bedfordshire in weather conditions which could be described as marginal, or at least marginal for that type of aircraft.
    "Your story, to a greater extent, changed this, and we carried out an investigation earlier this year into the aborted bomber operation of 15 Dec. 1944. Because the operation was aborted, there is no raid report on B(omber) C(ommand) records, as would have been customary with a completed operation. We did find reference to the intended course."
    The Miller flight took off from Twinwood Farms, near Bedford, 50 miles northwest of London, at 1:55 P.M. Greenwich War Time. The pilot filed no flight plan and his course is unknown. Mr. Munday said today that, although the band leader was flying to France at the time the R.A.F. squadron was returning from its aborted mission, they could have been miles apart.
    Victor Gregory, the pilot of the R.A.F. plane, now living in Westonsuper-Mare, England, answered Mr. Ross's advertisement, thinking it had something to do with a reunion. He confirmed Mr. Shaw's story.
    The bombardier, Ivor Pritchard, who would have had the best view, asked the navigator whether he could see the bombs exploding, Mr. Gregory recalled. The pilot said Mr. Shaw "got up and looked out of the little dome and spotted this aircraft, a Norseman.
    "The rear gunner, who was looking around all the time, saw it tip up and go into the sea," Mr. Gregory said. "When these bombs go off, they cause a lot of explosion." The gunner, Harry Fellowes, then asked on the intercom, "Did you see that kite go in?" A kite, Mr. Gregory explained, was slang for a [small] plane.
    Mr. Pritchard died in 1983, according to Mr. Ross, but Mr. Fellowes may still be alive, and his former crew members are anxious to talk to him and to the other crew members: Robert O'Hanlan, the radio operator; Derek Thurman, the engineer; Derek Arnold, the mid-upper gunner; and Frank Appleby, the mid-under gunner. They also want to locate the crews of other bombers in the area.
    When asked why it had taken so long for him to come forward, Mr. Gregory said he had forgotten the incident until contacted by Mr. Ross. "When we got back from that raid," he explained, "it was an aborted raid, so we didn't go in for our normal debriefing. Don't think me unsympathetic or callous, but when I heard of the plane going down, I would have said that he shouldn't have been there--forget him. My own concern was getting my own airplane home safely. We were fighting a war, and we lost thousands of planes. We had some pretty grim raids after that, and they didn't announce Miller's death until later. It had gone completely from my mind." Mr. Miller was first reported missing on Dec. 24, 1944.
    Mr. Shaw said that he had become interested after he saw the film, 'The Glenn Miller Story', in 1954, checked his log book, and realized the downed plane might have been carrying the band leader. He was rebuffed when he approached newspaper reporters at the time and forgot about it until he saw the movie again, years later, in South Africa.