The US today announced extra aviation security measures, including enhanced random screening and additional federal air marshals on certain routes. The measures come in the wakr of intelligence warning that al-Qaeda in Yemen is planning more attacks following the botched Christmas Day attempt to blow up an American plane. <br/><br/>Secretary, Homeland Security, Janet Napolitano said in Washington that in view of the Christmas Day attempt when al-Qaeda-trained Nigerian bomber Umar Farouq Abdulmutallab tried to blow up a Detroit-bound plane, the US must remain vigilant about the continued threat the country faces from the terror outfit. She said, as a result of these measures, travellers should allot extra time when flying, particularly into the United States from overseas. Her remarks came as intelligence officials warned that al-Qaeda affiliates in Yemen are planning further attacks following the failed Christmas Day bombing.<br/><br/>The new measures follow a wide-ranging security review ordered by President Barack Obama.