Flight diverted by mother's parental kidnapping attempt

Story here. Excerpt:

'A Beijing-bound United Airlines flight returned to Washington's Dulles International Airport Thursday evening because of a child custody investigation.
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The Federal Bureau of Investigation had received an alert that a mother on that flight was allegedly taking her child out of the country illegally, an FBI spokesman told CNN.
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"The mother was taken into custody on suspicion of committing an international parental kidnapping and the child was reunited with the father. The grandmother was not detained."
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After separating and starting divorce proceedings in 2013, Liu and William J. Ruifrok III were awarded joint custody of their 4-year-old son, who was born in China and is a dual U.S.-Chinese citizen, the complaint stated. The 2014 custody agreement doesn't allow either party to travel outside of the United States without "express written and notarized consent of the other party, provided in advance of the trip," according to the complaint.'