But Alex Goldfarb, a friend of Mr. Litvinenko who is acting as a spokesman for his family, said the discovery of radiation on the airplanes pointed squarely at Moscow’s involvement.  “We still believe this is a murder perpetrated by agents of Russia’s intelligence services,” Mr. Goldfarb told reporters outside the coroner’s court in St. Pancras, where an inquest into Mr. Litvinenko’s death opened today.  British Airways posted on its Web site a list of the flights made by the planes that were examined by investigators.  “If you look at the flight numbers BA have released, the first flight they are interested in was five days before the poisoning — the Moscow-Heathrow flight on Oct. 25,” Mr. Goldfarb said. “This tells you that the police are looking for the ways of delivery of this material into London, and this reinforces the theory that the origin of this material that killed Alexander was in Moscow.”  If that is the case, and it is by no means clear that it is, then it would follow that whoever brought the polonium into Britain was himself unknowingly contaminated with minute traces of it, enough to leave a trail that sensitive equipment could pick up later.  Dr. Mark Hill, a physicist at the Medical Research Council’s Radiation and Genome Stability Unit, said that while scientists in a lab would take utmost care to prevent radiation from leaking out, it was possible that someone paying less scrupulous attention might end up with traces of the material on, for instance, his hands or clothing.  “If you have a piece of contamination on the person or on an object, if you take it around, the contamination would spread,” he said in an interview. For example, he said, “If you’re transferring it from one container to another and for whatever reason you get some contamination outside of the bottle, if you’ve got it on your hand, everything you subsequently touch might leave a small trace.”  Investigators have still not said for sure whether the trail of radiation around London was left by Mr. Litvinenko alone, by someone else who handled the polonium 210 that poisoned him, or by someone who came into contact with him after he became contaminated.  Dr. Philip Walker, a professor of physics at the University of Surrey, said in an interview that a substance like polonium 210 was most likely to be excreted in urine or feces and could conceivably have been spread in minuscule doses as Mr. Litvinenko traveled around London. But he was hard-pressed to conjure a surefire scenario.  “There isn’t a lot of experience in giving people doses of polonium 210,” he said.  The British Airways planes involved made an estimated 221 flights to 10 locations from Oct. 25 to Nov. 29, carrying some 33,000 passengers, the airline said. “It’s a matter of giving them reassurance to inform them that the danger is low,” the spokesman said in an interview, asking that his name not be used in accordance with company policy. British citizens worried about their health were being advised to telephone the national health service, he said, and passengers outside Britain who were on the affected flights were told to check with their physicians.  The British home secretary, John Reid, said some 1,700 people had telephoned the health service as of Wednesday night, and that none had tested positive for radioactivity.  In Moscow, the newspaper Kommersant reported that Andrei Lugovi, one of the two Russians who met with Mr. Litvinenko at the Millennium hotel on the day he became sick, said he had flown on one of the contaminated British Airways jets on Nov. 3.  Mr. Lugovi has denied poisoning Mr. Litvinenko.  The poisoning affair widened in other ways. Doctors treating Yegor T. Gaidar, a former prime minister and academic who fell ill in Ireland the day after Mr. Litvinenko died, concluded that he had been poisoned, though the substance remained unknown, Mr. Gaidar’s spokesman said.  “They can say he was poisoned, but they cannot say what the substance was,” the spokesman, Valery A. Natarov, said in a telephone interview. “It was not natural. It was not some sort of food or drink.”  Yekaterian Y. Genieva, director general of the Russia state library for Foreign Literature, traveled with Mr. Gaidar to Ireland, where he participated in a conference on Russian and Irish culture. She said they had arrived on Nov. 23 on a flight from Moscow, via Budapest, and shared breakfast on the morning he fell ill.  She said he had fruit salad and tea, served by an elderly woman at the site of the conference, the National University of Ireland, Maynooth.  “I say this because this was the only other person he encountered” who was not part of the group, she said in a telephone interview.  Mr. Gaidar complained that he felt ill and made arrangements to return to Moscow, but proceeded to give a lecture and present his new book, “The Death of Empire: Lessons for Modern Russia,” an economic history of the collapse of the Soviet Union.  Ms. Genieva recalled that Mr. Gaidar excused himself from a discussion. She found him in a corridor, vomiting and bleeding from his nose. She waited with him until an ambulance came. He was hospitalized and returned to Moscow two days later.  She declined to speculate on his illness, but added, “It was not normal at all. There were no obvious signs” of anything untoward.  Mr. Natarov said that Mr. Gaidar’s doctors — at an undisclosed hospital in Moscow — would try to establish a cause with additional tests, perhaps by next week.  On Wednesday, Anatoly B. Chubais, an ally of Mr. Gaidar and chairman of Russia’s electric monopoly, said that Mr. Gaidar appeared to have escaped an attempt on his life and linked the case to Mr. Litvinenko’s death and to the murder of the journalist Anna Politkovskaya in October.  Steven Lee Myers contributed reporting from Moscow.
In the latest discoveries after the poisoning of an ex- K.G.B. agent, radiation was found at 12 sites in Britain.