An airline passenger from Nigeria who said he was acting on al-Qaida's instructions set off an explosive device in a failed terror attack on the plane as it was preparing to land.
Northwest Airlines Flight 253 with 278 passengers aboard was 20 minutes from the airport at Detroit, Michigan, yesterday, when the device, that sounded like a firecracker, exploded, witnesses said.
One passenger jumped over others and tried to subdue the man and shortly afterwards the suspect was taken to a front row seat with his trousers cut off and his legs burned.
The White House said it believed it was an attempted act of terrorism and stricter, unspecified, security measures were quickly imposed on airline travel.
Law enforcement sources identified the suspect as Umar Farouk Abdul Mutallab. Others had slightly different spellings.
One source said the man claimed to have been instructed by al-Qaida to detonate the plane over US soil.
"It sounded like a firecracker in a pillowcase," said Peter Smith, a passenger from the Netherlands.
"First there was a pop, and then (there) was smoke."
One passenger was believed to have been burned as he tackled the suspect.
Mr Smith said the passenger, sitting opposite the suspect, climbed over others, went across the aisle and tried to restrain the man.
The incident was reminiscent of British bomber Richard Reid, who tried to destroy a transatlantic flight in 2001 with explosives hidden in his shoes, but was subdued by other passengers. Reid is serving a life sentence.
US Rep Peter King, ranking Republican member of the House of Representatives Homeland Security Committee, said the flight began in Nigeria and went through Amsterdam en route to Detroit.
A statement from Delta, which acquired Northwest, said: "Upon approach to Detroit, a passenger caused a disturbance onboard Northwest Airlines Flight 253. The passenger was subdued immediately and the crew requested that law enforcement meet the flight upon arrival.
"The flight, operated by Northwest using an Airbus 330-300 aircraft with 278 passengers on board, landed safely. The passenger was taken into custody and questioned by law enforcement authorities."
US President Barack Obama was notified of the incident and discussed it with security officials, the White House said. It said he was monitoring the situation and receiving regular updates from his holiday spot in Hawaii.
There was nothing out of the ordinary about Flight 253 until it was on final approach to Detroit, said Federal Aviation Administration spokeswoman Elizabeth Isham Cory.
That is when the pilot declared an emergency and landed shortly afterwards at 12.51pm local time (5.51pm Irish time).
One US intelligence official said the explosive device was a mix of powder and liquid that failed when the suspect tried to detonate it.
The suspect, who was questioned last night, was being held and treated in a hospital in Ann Arbor, Michigan, an intelligence source said.
An official determination of a terrorist act would have to come from the US attorney general.
The White House was co-ordinating briefings for President Obama through the Homeland Security Department, the Transportation Security Administration and the FBI.
A law enforcement source said the explosives may have been strapped to the man's body, but investigators were not immediately certain, partly because of the struggle with other passengers.
Syed Jafri, a US citizen who had flown from the United Arab Emirates, said he was seated three rows behind the suspect and saw a glow and smelled smoke. Then, he said, "a young man behind me jumped on him".
"Next thing you know, there was a lot of panic," he said.
The Homeland Security Department said: "We encourage those with future travel plans to stay in touch with their airline and to visit www.tsa.gov for updates."
The department encouraged travellers to be observant and aware of their surroundings and report any suspicious behaviour.
Mr Smith said while he was leaving the plane, he looked at where the man had been sitting and saw a pillow that seemed to have been burned.
Melinda Dennis, who was seated in the front row of the plane, said the suspect was brought to the front row and seated near her. She said his legs appeared to be badly burned and his trousers were cut off.
She said he was taken off the plane handcuffed to a stretcher.
US government officials said there would be heightened security for both domestic and international flights at airports across the country, but the intensified levels would probably be "layered", differing from location to location depending on alerts, security concerns and other factors.
Passengers could expect to see more screening, bomb-sniffing dog and officer units and behavioural-detection specialists at some airports.
A spokeswoman for police at Schiphol airport in Amsterdam would not comment about the case or security procedures at the airport for Flight 253.
Schiphol, one of Europe's busiest airports with a heavy load of passengers from Africa and Asia to North America, strictly enforces European security regulations including only allowing small amounts in hand luggage that must be placed inside clear plastic bags.
In 2003, al-Qaida leader Osama bin Laden purportedly marked Nigeria for liberation in a recording posted on the internet, calling on Muslims in the oil-rich country to rise up against one of the "regimes who are slaves of America".
But links to al-Qaida remained rare, though security forces claimed to break up such a linked terror cell in November 2007.
Security at Nigeria's two major international airports in the capital Abuja and in its mega-city Lagos remain a point of concern.
Uniformed police often focus their time on keeping hagglers and taxi drivers out. Bags quickly pass through X-ray scanners and those watching incoming passengers do not typically conduct tests for explosive residue on passengers' carry-on baggage nor shoes.
At the gate, airline workers often check passengers again with handheld metal detectors before they board their flight.
Delta, which is days away from obtaining a single operating certificate from the FAA to fully integrate itself and Northwest, has been hosting military personnel who have to travel over the holidays in a lounge at the Detroit airport.
Nigeria's information minister, Dora Akunyili, condemned the attempted bombing. She said the government has opened its own investigation into the suspect and will work with US authorities.
“We state very clearly that as a nation we abhor all forms of violence,” Akunyili said in a statement issued today.