It was a startling scene for one passenger traveling through Washington Dulles International Airport near the nation’s capital on Wednesday: security personnel waving a long line of passengers through a checkpoint with instructions to ignore many common post-9/11 rules.

The crowd was allowed to keep their shoes on. They were not required to remove laptops from their carry-on bags. And they did not have to step inside body-scanning capsules that require an awkward wide stance and hands in the air.

They were put through metal detectors, but the female passenger who alerted U.S. News to the scene says she felt unsafe and confused by the abrupt break in long-running airport security procedures.

“It was a ZOO. As bad as Christmas or Thanksgiving,” the tipster writes in an email. “It really felt crazy and like they were just trying to cut the wait down so much that they were throwing all rules out the window.”

A spokesman for the Transportation Security Administration, Mike England, confirmed key details of the account but says Americans who see similar scenes should not be concerned.

England says the passenger, who asked not to be identified by name, was discreetly sniffed by a trained explosives-detecting dog, which made the three common security measures unnecessary.

“What the explosive detection canines do is screen passengers and their carry-on luggage for explosives – and once a passenger has been screened by one of those canines, they no longer need to take off their shoes or take out their laptops or go through the body scanner, because the whole point of doing those things is to look for explosives,” he says.

“It happens very quickly. The canines can just go through a line and screen everyone that fast.”

Passengers sniffed by a dog get perks similar to those offered to vetted fliers who register with the TSA's PreCheck program, who also are allowed to wear shoes through checkpoints and keep their laptops in bags before they are scanned by an X-ray machine.

England says he does not have information to confirm that Dulles experienced unusually long lines on Wednesday. But he says explosive-detection canines are dispatched at major airports around the country – such as large international airports in Chicago and Atlanta – and that the TSA tries to have them work during peak hours.

The new practice may be greeted with enthusiasm by TSA skeptics who noisily dismiss some airport security measures as intrusive and unnecessary theater intended to create a false impression of safety.

But can a dog truly ensure nobody’s standing on a shoe bomb, lugging an incendiary laptop or packing explosives in their underwear?

Yes, England says. The dogs have a hit rate of more than 90 percent, he says, though he says the specific explosives they are trained to detect cannot be publicly disclosed for security reasons.

In April, Reuters reported that the TSA has 222 explosives-detecting canine teams, 140 of which are trained to sniff passengers.

The source, who was alarmed by what she believed was a corner-cutting approach to security says, “I do feel much safer” after learning a trained dog performed explosives screening. She confirmed seeing a dog stationed between an ID-checking counter and metal detector machines.

It’s unclear if most members of the public would feel comfortable with a dog supplanting existing screening practices. But following news reports about extremely long lines at major airports this spring, more dogs may be on their way.