There have been a number of attacks and attempted attacks on American soil since 11 September, 2001. Here are some of the most significant:
DETROIT PLANE BOMB CASE, 25 DECEMBER 2009
Mr Abdulmutallab is charged with attempted murder of 290 people
As a Northwest Airlines flight approached Detroit on Christmas Day, Nigerian national Umar Farouk Abdulmutallab is accused of lighting a makeshift bomb smuggled aboard in his underwear. The device fizzled and smoked but did not detonate, and passengers and crew subdued the suspect. Mr Abdulmutallab, who was burnt in the attempt, is currently in US custody awaiting further legal proceedings. A not guilty plea has been entered by his lawyers. Mr Abdulmutallab's father, a prominent Nigerian banker, sought to warn US officials about his son ahead of the alleged attempt.
FORT HOOD SHOOTINGS, 5 NOVEMBER 2009
A gunman killed 13 soldiers and wounded dozens more at the Fort Hood army base in Texas. Army psychiatrist Maj Nidal Hasan, an American Muslim of Palestinian descent, has been charged with murder in the attacks, and military prosecutors are seeking the death penalty. Officials say that before the attack he was in contact with a radical American-born Islamist cleric based in Yemen.
PLOT TO BOMB NEW YORK SUBWAY, 2009
Najibullah Zazi, an Afghan immigrant who worked at a New York City coffee stand and later drove an airport shuttle in Colorado, and New Yorker Zarein Ahmedzay have pleaded guilty to plotting to bomb the New York subway system last year. A third suspect awaits trial. US authorities say the plot was hatched by senior al-Qaeda leaders in Pakistan.
A group of young Yemeni-American men in Lackawanna, New York state, pleaded guilty in 2003 to aiding a terror organisation and received prison sentences. Prosecutors accused the six of training at al-Qaeda camps in Afghanistan in the months before the 11 September, 2001 attacks. Their defence attorneys said the men had no advance knowledge of the attacks and had left the camp early because they were disturbed by the rhetoric they heard there.
EL AL TICKET COUNTER, LOS ANGELES INTERNATIONAL AIRPORT, JULY 2002
A gunman later identified as 41-year-old Egyptian immigrant Hesham Mohammed Ali Hadayet opened fire at the Los Angeles International Airport ticket counter of Israeli airline El Al, killing two people and wounding several others. He was shot and killed by a security guard. Federal law enforcement officials later said he had acted alone and had no connections to international terror organisations.
ACCUSED 'DIRTY BOMBER' JOSE PADILLA
Most recent US terror attempts were plotted by US citizens or legal residents
A former Chicago gang member, Mr Padilla was arrested at O'Hare International Airport in May 2002 on a material witness warrant. The US government accused him of plotting to detonate a radioactive "dirty bomb" on US soil. After years of detention during which he was transferred between military and civilian courts, Mr Padilla was convicted in January 2008 of less specific charges of support for terrorism and conspiracy. The judge in the case rebuked the Bush administration for its treatment of Mr Padilla during his detention.