The United States is increasing security for air travel across the country after a Nigerian man set off a small explosion aboard a flight bound for the U.S. city of Detroit.  White House officials are calling it "an attempted act of terrorism."  

The incident happened just about twenty minutes before Northwest Airlines Flight 253, flying from Amsterdam, landed in Detroit.

"We heard a loud pop and a bit of smoke and then some flames, and then yelling and screaming," one passenger said.

"It was scary," said another.  "It was a loud firecracker that went off, and there was a fire in the plane after a few seconds. It was very scary for everyone," the passenger said.

One passenger immediately sprang into action when it appeared something was wrong.

"There was one guy who sat on the other side, on the right side of the wing," recounted a passenger who observed the heroic act. "This was on the left side of the wing. He jumped over all the other people and he took care of it, so the fire went out."

No one was injured and once the plane landed the suspect was taken into custody.  

U.S. counterterrorism officials say he is a 23-year-old Nigerian named Umar Farouk Abdul Mutallab and that he was trying to blow up the plane.  They also say his name does appear on a U.S. intelligence watch list, but  not  on a no-fly list that would have prevented him from boarding the flight.

Mutallab suffered third-degree burns, but still managed to tell investigators he was acting on behalf of al-Qaida.  Those claims have yet to be confirmed.  

"We have real concerns here, because we know that Nigeria is a source of terrorist activity, al-Qaida connected activity," said New York Congressman Peter King, a ranking Republican on the Homeland Security Committee.

The Republican congressman said critical questions will have to be answered, and answered quickly.

"How he was able to get on in Nigeria, what happened in Amsterdam, which is a visa waiver country, how he was able to get through and make it this far with the devices he had, these are all issues that have to be resolved."

The U.S. Department of Homeland Security says additional security measures are being put into place for all flights, and is encouraging passengers to be observant and report any suspicious activity.

IntelCenter, a U.S.-based terrorism monitoring group that works with the U.S. government, says the incident appears to be a serious attempt against the United States, with connections to Yemen and Nigeria.  It also says the possibility of additional attempts over the next day or two cannot be ruled out.