"I believe the TSA is having a credibility problem," he said. "If you hate something, you're going to have a worse time doing it. If people don't trust something and hate it, then it goes less well."

A study published in Security Journal last year found that passengers in the United Kingdom had a higher opinion of whole-body scanners after they were presented with unbiased information about them, including risks and sample images. They found them fast and less intrusive than pat-downs. Not informing passengers about scanners can open the door to misinformation and critics, the study's authors said, and hurt the long-term acceptance and legitimacy of airport security.

What will make customers happy, though, depends on their complaints.

Schneier said he'd be happier if the TSA ran airport security that looked more like it did before September 11, 2001, before liquid bans, body scanners and shoe removal. He calls the TSA's best-known processes "security theater" but said there's no political will to eliminate it.

"Everyone complains about the TSA, but nobody really wants to be on the hook for getting it wrong," he said.

Elliott, the consumer advocate and author of "Scammed: How to Save Your Money and Find Better Service in a World of Schemes, Swindles and Shady Deals," said he'd feel better about the TSA if it eliminated its Visible Intermodal Prevention and Response, or VIPR, teams at train stations and NFL games and instead stuck to airport security. When he's in line to fly, he wants better explanations about TSA procedures and to know that more money is steered toward intelligence instead of "unconstitutional" scans and pat-downs.

"It's a matter of using billions of dollars in a smarter way," he said. "There's always going to be people that say, 'If you take a step back, you're going to create the next 9/11.' Those are paranoid voices, and they're always going to be there. I have to listen to the rational voices that say we've gone too far."

The Barry family in Denver wants TSA agents trained so everyone with a medical device or condition can make it through security checkpoints safely, said Sandra Barry, whose daughter's insulin pump was replaced after its ill-fated trip through Salt Lake City's airport.

Barry said they respect that TSA officers are highly trained and low-paid and "have an important job to do." She can even understand why security officers wanted to send Savannah through the scanner: It was busy, scanners are quick, and the public usually isn't thrilled about security agents patting down teenage girls.

But the Barry family isn't flying again until they're confident their kids -- both of whom have Type 1 diabetes -- will have pumps that work beyond the checkpoint. Insulin pumps can cost $8,000 to $10,000, Barry said, and it can be hard for pump users to switch back to injections. The family will be driving to their summer vacation destinations this year.

The agency said last month that it would respond directly to the Barry family and that it regularly works with disability and medical condition advocacy groups to adapt screening procedures.

Indeed, Barry said, they spoke with TSA officials on a conference call this week and are reviewing a proposal they hope will make flying easier for diabetics. So far, Barry said, the TSA has been slow but responsive.

"We could be their best advocate. This could be a total turnaround and nice PR for them," Barry said. "Right now, our relationship is really amicable, and we'd like to keep it that way."