Washington: F-16 fighter jets scrambled twice after reports of air passengers acting suspiciously on two flights as America marked the 10th anniversary of 9/11.
However, officials were quick to reassure that what happened on American Airlines Flight 34 from Los Angeles to New York Airlines and the Frontier Airlines Flight 623 from Denver to Detroit has no nexus to terrorism.
In the first incident involving three passengers, authorities sent two F-16 jets to shadow the flight until it landed safely at John F Kennedy International Airport in New York at 4.10 pm, according to the Transportation Security Administration spokesman Greg Soule.
In the second incident, crew members noticed two men acting suspiciously. One spent about 20 minutes in a bathroom in the back of the plane while the other waited in a forward galley before using the restroom, also for 20 minutes, CNN said citing Frontier spokesman Peter Kowalchuk.
Meanwhile, President Barack Obama on Sunday concluded ceremonies of remembrances of Americans who died in the September 11, 2001 terrorist attacks on New York and the Pentagon in Washington with a message of unity and resolve for the years ahead.
"These past 10 years underscore the bonds between all Americans. We have not succumbed to suspicion and mistrust," Obama said at the "Concert for Hope" at the Kennedy Centre in Washington. "It will be said of us that we kept that faith; that we took a painful blow, and emerged stronger."
Earlier, thousands gathered at New York`s ground zero, site of the World Trade Centre, and stood still in silence, some crying as they listened to the names of victims attacks read aloud.
Parallel commemoration ceremonies also took place in Washington-where mourners observed a moment of silence at 9.37 am, the moment American Airlines Flight 77 struck the Pentagon, killing 184 people-and in Shanksville, Pennsylvania, where passengers aboard United Flight 93 are believed to have thwarted a plot to drive the plane through the US Capitol dome and eventually caused the plane to crash in a field.