The more that is disclosed about the alleged airline bomber from Nigeria, the clearer it becomes that the aspiring martyr never should have been allowed to board a commercial jetliner bound for Detroit.

President Obama now says a "systemic failure" occurred among U.S. intelligence and security agencies prior to the incident on Christmas Day.

That's a 180-degree turn in the right direction from his administration's earlier mystifying claim that "the system worked."

But recognizing failure, however grudgingly, is easier than correcting it. Questions are multiplying about how the suspect, Umar Farouk Abdulmutallab, was able to evade extra scrutiny for months before he nearly brought down a commercial airliner.

One of the most basic security lapses involves the man's U.S. visa, which was issued to him in June 2008. That document allowed him to travel to the United States for two years.

Abdulmutallab's father walked into a U.S. embassy in Nigeria on Nov. 19 to ask for help in finding his son. He told officials that his son had disappeared in Yemen, a known terrorist hot spot. He also said the young man had cut off all ties to his family, and that he had become radicalized in Islam.

The next day, this information was shared with officials at the Department of Homeland Security, the FBI, and the State Department. The National Counterterrorism Center put Abdulmutallab's name on a terrorist watch list, but officials didn't believe the information merited putting him on a "no fly" list or a list that called for heightened screening at airports.

Those decisions were questionable, but even worse, nobody at the State Department thought it important to point out that Abdulmutallab already possessed a U.S. visa. The State Department had the authority to revoke his visa or put a hold on it. Instead, officials there apparently decided just to wait until his visa came up for renewal next summer to give him a thorough review.

U.S. officials also should have been aware that Britain had denied Abdulmutallab a visa in May and had placed him on a watch list. It's not clear yet whether British authorities failed to share that information, or whether U.S. officials ignored it. Either way, communication channels need to be improved.

The issue of airport security technology also needs to be reviewed. Costly screening machines, such as so-called "body imagers," can detect nonmetallic objects on a person's body, including the powder PETN explosive that Abdulmutallab was carrying.

The federal Transportation Security Administration now has 10 such screening systems in development. There needs to be an independent assessment of which machines are the most effective, and how and where they would be best deployed. Five years ago, the 9/11 Commission urged the TSA to make this issue a priority.

U.S. security officials protest they didn't have enough solid information on Abdulmutallab prior to Christmas Day. But they had been alerted. There won't always be warnings about terrorist attacks. When authorities do receive a heads-up, it's all the more imperative that they pursue the information - and do it quickly.