BEIJING - China allowed a blind legal activist, Chen Guangcheng, to leave a hospital in Beijing on Saturday and board a plane bound for the United States, a move that could signal the end of a diplomatic standoff between the two countries.Chen's escape from house arrest in northeastern China last month and subsequent stay in the US embassy caused huge embarrassment for China and led to a diplomatic rift while US Secretary of State Hillary Clinton was visiting Beijing for talks to improve ties between the world's two biggest economies.Police at the airportUnited Airlines flight UA 88 departed around 5.50 p.m. (0950 GMT), with police officers and plainclothes officers following passengers down the mobile corridor leading to the plane's door.The cabin crew waited for passengers to take their seats before closing the curtain to the front section, where the business class seats were located, a Reuters witness said.Chen had earlier told Reuters he was at the airport along with his wife, two children and hospital staff and he believed he would be put on a flight to the United States.Two police cars were stationed below the walkway to the plane, and about 10 security officials in plainclothes circulated around the airport.Passengers at the gate to Chen's flight appeared not to know that he would be on the same flight."If our country is a body, his plight is like a sickness that in the future will help the body to protect and strengthen itself," said Xi Jingwen, who was awaiting to board a flight to the United States, when asked about Chen Guangcheng.Chen's confinement, his escape and the furor that ensued have made him part of China's dissident folklore: a blind prisoner outfoxing Communist Party controls in an echo of the man who stood down an army tank near Tiananmen Square in 1989.The Chen case comes at a tricky time for China, which is engaged in a leadership change. The carefully choreographed transition has already been knocked out of step by the downfall of ambitious senior Communist Party official Bo Xilai in a scandal linked to the apparent murder of a British businessman.Chen's supporters welcomed his departure, saying he had indicated that he would like to return to China."I even told him...that he has to do a repeat of him scaling walls. If not, we wouldn't be able to believe it," Nanjing-based activist He Peirong said of her earlier conversation with Chen. She was one of six activists who drove Chen from Shandong to Beijing after his escape.Phelim Kine, senior Asia researcher at New York-based Human Rights Watch, said "getting Chen Guangcheng and his family on a plane is the easiest part of this saga."The harder, longer term part is ensuring his right under international law to return to China when he sees fit," Kine said in an emailed statement.Kine urged Western countries to ensure that Chen's relatives, friends and supporters secured due protection.The US embassy had earlier thought it had stuck a deal to allow Chen to stay in China without retribution, but that fell apart as Chen grew worried about his family's safety. He changed his mind about staying and asked to travel to the United States.Human rights are a big factor in relations between China and the United States, even though Washington needs China's help on issues such as Iran, North Korea, Sudan and the global economy.The village of Dongshigu, where Chen's mother and other relatives remain, is still under lockdown.Chen's nephew, Chen Kegui, was denied his family's choice of lawyers on Friday to defend a charge of "intentional homicide," the latest in a series of moves to deny him legal representation, and underscores the hardline stance taken against the blind dissident's family.The US State Department said he was en route to the United States, along with his wife and two children. He boarded a United Airlines flight bound for Newark.State news agency Xinhua said Chen had applied to study in the United States under legal procedures, in the first official account of Chen's activities, but made no mention of whether he had left the country. The Foreign Ministry said this month that Chen could apply to study abroad, a move seen as a way of easing Sino-US tensions on human rights.Chen's friend, Jiang Tianyong, cited the activist, one of China's most prominent dissidents, as saying that he and his family obtained their passports at the airport hours before he was due to board a flight."I'm obviously very happy," Jiang said. "When he boards the plane, he can finally say: 'I'm free'. At the same time, I feel a sense of regret because such a large country like China can't even tolerate a citizen like him to exist here."There was no immediate indication where Chen might pursue his studies, but New York University's law school has previously offered him a position as a "visiting scholar."A statement by State Department spokeswoman Victoria Nuland struck a conciliatory note, saying Washington was "looking forward" to Chen's arrival."We also express our appreciation for the manner in which we were able to resolve this matter and to support Mr. Chen's desire to study in the US and pursue his goals," it said.Beijing has accused the United States of meddling in its affairs in the Chen case.Chen's abrupt departure for the airport came about three weeks after he arrived at the Chaoyang Hospital from the US embassy, where he had taken refuge after an escape from 19 months under house arrest in his home village.Chen, 40, who taught himself law, was a leading advocate of the rights defense movement. He gained prominence by campaigning for farmers and disabled citizens and exposing forced abortions.He was jailed for a little over four years from 2006 on what he and his supporters say were trumped-up charges designed to end his rights advocacy.He had accused Shandong officials in 2005 of forcing women to have late-term abortions and sterilizations to comply with strict family-planning policies. Authorities moved against him with charges of whipping up a crowd that disrupted traffic and damaged property.Formally released in 2010, he remained under house arrest in his home village, which officials turned into a fortress of walls, security cameras and guards in plain clothes.