WASHINGTON - New security measures are scheduled to go into effect Monday on all international flights to the U.S.
The changes come in the wake of the botched bombing of a Northwest Airlines flight on Christmas Day.
Security Scare at Newark Airport
Minus a few delays, air traffic was back to normal at Newark's Liberty Airport in New Jersey after a security breach prompted a lockdown.
"We were inside the plane and then they announced that we had to go back through security so we went back to the gate," one passenger said.
CBN News Terrorism Analyst Erick Stakelbeck has more on the security threats facing America. Click play for his comments.
An unidentified man went the wrong way through a security checkpoint, forcing everyone to be re-screened.
The scare came as on edge security officials were about to launch new measures to make air travel safer.
Starting Monday, the U.S. Transportation Security Administration will require extra screening for passengers from or traveling through countries listed by the State Department as sponsors of terrorism. Those countries include Iran, Syria and Cuba along with 10 other countries of interest.
The new measures include full body scans or - for those who refuse - a pat-down by a TSA officer. The new rules are in response to the failed Christmas Day airline bombing by a Nigerian who was trained by al Qaeda in Yemen.
Al Qaeda in Yemen
Yemen - considered a key U.S. ally though not always reliable - has become a haven for terrorists taking advantage of a weak central government and widespread poverty.
"We're working very closely with the Yemeni authorities to address the threat that is out there," said John Brenna, White House advisor on counterterrorism.
"But again," he added, "it just demonstrates that al Qaeda is determined to carry out these attacks and we're determined to thwart those attacks."
Meanwhile, for the second day the British and American embassies in Yemen closed citing an active threat from al Qaeda.
Part of the problem isn't just foreign fighters fleeing war zones in Pakistan or Afghanistan. Some of those coming to Yemen include former prisoners at Cuba's Guantanamo Bay prison. Out of the 500 or so prisoners released from the facility, the Pentagon says approximately 60 have returned to the battlefield.
"These are people that were held in Gitmo and have been returned and have now gone back to the battlefield," Rep. Peter Hoekstra, R-Mich., said.
And more of them appear to be resurfacing in Yemen.
Sen. Joe Lieberman, I-Conn., told ABC's This Week, "One of our American personnel there said to us -- and I thought quite wisely -- that Iraq is yesterday's war, Afghanistan is today's war, and if we don't act preemptively, Yemen will be tomorrow's war."