Washington ( CNN ) -- Air travelers are n't likely to notice visible security changes as a result of a terrorism threat alert issued Friday by the State Department . The extraordinary global travel alert advised that al Qaeda may launch attacks in the Middle East , North Africa and beyond in coming weeks , and the U.S. government prepared to close 21 embassies and consulates from Algeria to Bangladesh on Sunday as a precaution . Three sources told CNN that the United States has information that Yemen-based al Qaeda in the Arabian Peninsula was in the final stages of planning for an unspecified attack . `` U.S. citizens are reminded of the potential for terrorists to attack public transportation systems and other tourist infrastructure . Terrorists have targeted and attacked subway and rail systems , as well as aviation and maritime services , '' the State Department 's alert said . Airlines said they have n't changed operations as a result of the alert . The alert is focused on U.S. citizens traveling abroad , and the State Department suggested that travelers register with its Smart Traveler Enrollment Program , also known as STEP , which allows them to receive updated security information . Airlines for America ( A4A ) , the airline industry trade group , said is monitoring the situation and suggested that passengers could also sign up for travel notifications from their airlines . Delta Air Lines , which has one daily roundtrip flight between JFK Airport and Tel Aviv and one between Atlanta and Dubai , said it is operated with `` Business as usual , for now . '' United Airlines , which flies to North Africa and the Middle East , says there have been no flight schedule changes as the result of the warning . It says it is monitoring the situation and keeping in regular contact with the Transportation Security Administration and State Department . It is n't offering waivers for travelers wanting to change their flight , but that policy could change as the airline receives additional information . American Airlines said it has no flights to Africa or the Middle East , `` therefore we have nothing to waive . ''
Airlines say they have n't changed operations as a result of the alert . American Airlines : `` Business as usual , for now '' American Airlines : No flight schedule changes . United Airlines : No flights to Middle East , Africa , `` therefore we have nothing to waive ''