White House counterterrorism adviser John Brennan said on "This Week" this morning that the United States remains "especially vigilant" as the country marks the one year anniversary of the death of Osama bin Laden. But he also cautioned that a threat remains from al Qaeda's Yemeni affiliate, al Qaeda in the Arabian Peninsula.

"On a day that marks the one year anniversary of bin Laden being brought to justice, we are especially vigilant," Brennan said. "At this time we don't see any active plot that is underway."

I asked Brennan about the FBI warning this week that there are new efforts to target Western airports by al Qaeda in the Arabian Peninsula.

"They have demonstrated both the intent as well as the capability to try to carry out an attack," Brennan said. "They are continuing to try to, again,  carry out an attack against U.S. persons inside of Yemen as well as against the homeland."

Brennan also confirmed that Yemeni al Qaeda offshoot remains focused on targeting planes.

"Aviation has been a target, has been a traditional target of al Qaeda," Brennan said. " We need to maintain our vigilance, particularly overseas at these last points of departure."

Brennan noted that al Qaeda's capability has been "degraded significantly" and that bin Laden's death has made a "tremendous difference."

"It's taken away the founding leader of that organization who was … a symbol of al Qaeda's sort of murderous agenda worldwide," Brennan said. "And so, that has had I think a profound impact on the organization."

Brennan declined to address Republican criticism this week that the Obama campaign had politicized the killing of bin Laden in a campaign web video released Friday that suggested that Republican presidential candidate Mitt Romney may not have taken action against bin Laden.

"I don't do politics. I don't do the campaign. I am not a Democrat or Republican. I'm a counter-terrorism adviser to the president, Brennan said.

"All that I know is that the president made the decision when he was given the opportunity to take a gutsy decision, to carry out that raid with our Special Forces in Abbottabad, Pakistan," Brennan added. "We're safer today as a result."