WASHINGTON: The United States stepped up airport security as intelligence warned Al-Qaeda's affiliate in Yemen was planning more attacks to follow a failed Christmas Day bombing. Officials warned of "chatter" hinting at further strikes, as Homeland Security Secretary Janet Napolitano announced US-bound passengers would see increased airport security screening and armed marshals on flights. "We must remain vigilant about the continued threat we face from Al-Qaeda," Napolitano said. "We are taking an additional set of aviation security precautions to protect the American people. "Some of these measures include enhanced random screening, additional federal air marshals on certain routes and adding individuals of concern to our terrorist watch list system," she said without giving details. The measures follow a wide-ranging security review, ordered by President Barack Obama in the wake of Christmas Day attempt to bomb a trans-Atlantic jet. The Obama administration has faced fierce criticism for intelligence failures that allowed a young Nigerian man, to board a Detroit-bound airliner, allegedly armed with explosives sewn into his underwear. Yemen-trained Umar Farouk Abdulmutallab (UFA), 23, has been charged with attempted murder and trying to use a weapon of mass destruction on board the Northwest flight carrying 290 people from Amsterdam. Administration officials, who asked not to be named, said Thursday's measures responded to continued threats from Yemen-based operatives, despite a series US-backed strikes against senior militants based in the Gulf state. "We do know AQAP (Al-Qaeda in the Arabian Peninsula) sent UFA our way and it would not be prudent to suddenly think that threats like this have passed with his failure," an administration official told AFP. "I am sure there will be more security measure announcements in the future as we constantly review all the information available to us." Earlier this week Canada put its airlines and airports on high alert after receiving "specific information" about new threats. Meanwhile, Napolitano warned those visiting the United States of more airport delays. "Travelers should allot extra time when flying particularly into the United States from overseas," she said. Since the Christmas Day attack the United States had already ramped up security on flights from 14 countries, including Yemen. While laborious airport screening irks many visitors to the United States, tougher measures are popular with Americans, according to recent polls. On Thursday, a Quinnipiac University survey showed 63 percent of respondents said US anti-terror policies leaned too far toward protecting civil rights rather than national security. Industry representatives said the tougher measures had been widely expected. "We will have to come to grips with the reality that the air travel experience will be different," said David Castelveter of the Air Transport Association, a US trade association. "It will not be the same tomorrow as it is today. We will have to turn up earlier and pack differently." But there are lingering concerns that security related delays will cost already struggling airlines. To address those concerns Napolitano is scheduled to meet airline executives next week in Geneva, at the headquarters of the International Air Transport Association, an official for the organization said. The meeting will come as airlines report their forth quarter earnings, which are expected to reflect the full price of delays related to the thwarted Christmas Day bomb plot.