New technology exists that can see through clothing including underwear, to look for hidden devices. However, privacy concerns have held up its final approval. One such device is in limited use at SFO, but there is one one.
SFO and other U.S. airports have a big challenge ahead if and when domestic flights face the same level of security as international flights. SFO has one full-body scanner. It is one of only 19 in the country and it is in the international terminal. So-called "puffer machines" that sampled for explosives were put out of service when maintenance became a problem.
So, the lines seen on Monday could become more common.
"I think it's a big waste of time and if they knew they were going to do something they should have planned a little better," Mike Nyden told ABC7 News. "This line extends a quarter-mile behind us and just doesn't seem appropriate to me."
Some passengers were irritated while others were understanding.
"I think it's necessary and needed. It's only precautionary measures," said Nikki Peterson.
"It concerns me that I'm not going to make my flight because we have two more zigzags to go. And, this is like crazy," said Barbara Zenio.
Tighter security is already in place overseas.
"We were body frisked and every single piece of our carry-on bag was opened up, all little zips checked and everything was checked" recalled Robin smith who said she found the process rather intrusive.
A few passengers noticed that in-flight restrictions were eased Monday, such as remaining seated during the final hour of flight. One Dublin woman returning from Sydney was allowed to use the lavatory and a passenger from Hong Kong passenger saw the in-flight TV route map restored
"I much enjoy flying now than before because I know I'm in good hands right now, than before," Celine Wei said.
San Francisco International Airport spokesman Mike McCarron anticipates that security measures could ease or tighten in the days ahead.
"We've got to figure out how this all happened and piece it together," he said. "Where was the breakdown in the system? Was it Nigeria? Was it Schiphol Amsterdam? Until we get that, we really don't know what we're looking for and how to prevent it from occurring again."
This will make it very difficult for passengers to know what measures are in effect each day. Both domestic and international passengers will have to get to the airport early to face whatever security measures happen to be in place.