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.
She 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.