By this time, everyone knows that the system for keeping terrorists off airplanes has failed. It is time to do what President Obama has ordered: fix the defective screening system and intelligence procedures.

It is time, too, to close ranks, as we did in 2001 when terrorists hit the World Trade Center and the Pentagon and stop trying to make this crisis into a divisive political issue.

New alarms began on Christmas Day when a 23-year-old Nigerian man was able to board a Northwest Airlines flight in Amsterdam bound for New York on a multiple-entry visa with concealed explosive powders. This happened even though his father, a Nigerian banker, had reported that he was missing and may have been “radicalized” by a group in Yemen. Security officials knew that background, but information did not stop the bomb carrier or subject him to special screening.

Fortunately, he botched the attack. The bomb only partly exploded, and fellow passengers overpowered him. Instead of blowing a hole in the plane and killing the 300 passengers and crew, he alerted everyone to the need for tighter controls.

Part of the problem, as we now know it, is that members of al-Qaida’s terrorist network are busy devising ways to blow up our planes and disrupt other aspects of our vulnerable transportation, communication and production systems. They are inventive and resourceful. When we halted metallic weapons, they turned to liquids and powders.

Also, the screening systems did not work as intended, and intelligence information was not pieced together to focus on this young terrorist.

Heading off terrorists before they board the planes is only part of the solution. Some probably will always get past our preventive systems. So the hunt must continue to track down the al-Qaida leaders in Afghanistan, Pakistan, Yemen, Somalia and wherever else they are lurking and destroy their terrorist network.

The past and pending transfer of Guantanamo prisoners now has come into question. The Wall Street Journal, quoting Pentagon sources, on Wednesday named two leaders of the al-Qaida affiliate that has claimed responsibility for the Christmas Day attack as among at least 11 Saudi citizens who were released from Guantanamo in 2007 and have joined militant groups inside Yemen.

Both the Bush and Obama administrations have transferred Guantanamo detainees to Yemen in their efforts to close the base in Cuba. Six were released to Yemen in December. Three Republicans asked Mr. Obama last week to halt further transfers until the United States can be sure the detainees ”won’t return to the battlefield.”

After a minor flap in which the secretary of homeland security said “the system worked” and then corrected herself, and after three days in which the Obama administration gathered information, the president now has grasped the problem in all its dimensions and ordered reviews, accountability and improvement.

He is in charge, we’re all in this together, and we should all help make the system work for our mutual safety.