Did airport security fail in Christmas Day terror attempt?

It could have ended very differently on Christmas Day.

If the detonator that officials say Umar Farouk Abdulmutallab was carrying had worked, the explosives on his body had the potential to bring down Northwest flight 253.

And if the passengers and crew members on board the plane had not reacted so quickly to stop the fire and restrain the suspect, he might have been able to do more damage to the plane.

But there's another way of looking at the story as well. If the security screening process had denied Abdulmutallab access to the plane in Amsterdam or Lagos, he would never have had the opportunity to blow up the aircraft in the first place.

Three days after the alleged failed terror attempt over the skies of Detroit, questions are still being asked about the incident, and critics are concerned that 8 years after 9/11 airport security is still not tough enough.

Abdulmutallab's father, a wealthy Nigerian banker, reportedly told U.S. officials just last month that his son was a potential terror threat, but still he was not added to the no fly list. And he was apparently allowed to maintain his U.S. visa.

Senator Susan Collins (R-ME) said Sunday that Abdulmutallab's visa should have been revoked, or that he should have been physically searched before being allowed to board the plane. "This individual should not have been missed," she said. "Clearly, there should have been a red flag next to his name."

But Homeland Security Secretary Janet Napolitano seemed to disagree. "The system has worked really very, very smoothly over the course of the past several days," she said on "This Week" on ABC. Similarly, White House spokesman Robert Gibbs told CBS's "Face the Nation" that "in many ways, this system has worked."

The administration also faced criticism from Rep. Peter King (R-NY), who accused the administration of being "uncomfortable" in talking about terrorism and questioned why administration officials had not been more visible in reassuring the public immediately after the terrorist attempt.

Finally on Sunday, President Obama ordered a review of airport security measures, just as security was stepped up at major airports throughout the globe. By Sunday, security concerns were so high that airline officials from the same Northwest 253 flight from Amsterdam to Detroit that Abdulmutallab took two days earlier called in a threat to the plane after a different NIgerian man spent a long time in the restroom. Officials say the man was merely sick and the incident was determined to be a false alarm.

Still, many questions remain to be answered after the Christmas Day terror attempt and officials and the media will be looking for answers in the days to come. Among the questions...

How did a Nigerian man on a terror watch list board a plane for the U.S.?

Why weren't airport security officials tipped off by a man on the terror check list boarding a plane on an international flight with no checked luggage?

Who helped the suspect prepare the deadly explosive combination that could have brought down the plane?

Should officials have reacted more seriously when the suspect was identified by his father as a potential terrorist? Should he have been placed on a "no fly" list instead of a terror watch list?

Should Abdulmutallab's visa have been revoked after his father reported him?

Did the system work as it should have, as some government officials argued over the weekend, if the only thing that saved the flight was the faulty detonator and the quick action of passengers?

And just as importantly, how did a young, college-educated child of privilege become radicalized with anti-Western, Islamic fundamentalist ideas?