Ashley Brandt was all smiles last week when she went to board a flight home after a belated birthday trip to the Grand Canyon.

Then, standing in an airport security line in Phoenix, her jaw dropped.

According to Brandt, an agent with the Transportation Security Administration took a look at her D.C. license and began to shake her head. “I don’t know if we can accept these,” Brandt recalled the agent saying. “Do you have a U.S. passport?’

Brandt was dumbfounded, and quickly grew a little scared. A manager was summoned, she says. “I started thinking, ‘Oh my gosh, I have to get home. Am I going to get home?’ ”

The long Presidents’ Day weekend had been Brandt’s boyfriend’s first chance to make good on a December birthday promise to take Brandt to see the Grand Canyon. The two were now on their way back, and the next morning, a class would be waiting for Brandt at her Cleveland Park preschool a couple of miles north of the White House.

But the implication from the TSA agent seemed clear to Brandt: The District is not a state; TSA requires a state-issued ID to board a plane.

Nevermind that Brandt had used her brand-new D.C. license, the one marked “District of Columbia” over a backdrop of cherry blossoms, to board her flight to Arizona days earlier.

Brandt says the agent yelled out to a supervisor, working in adjacent security line. Are D.C. licenses valid identification?

Brandt says she could hear the response, “Yeah, we accept those.”

“She didn’t seem to know that it was basically the same as a state ID,” said Brandt, who had only recently traded her Maryland ID for one from the District. “D.C. is obviously not a state, but I didn’t ever imagine it would be a problem — I mean, the whole population of D.C. has to use these.”

Within a few minutes, Brandt said she was on her way to the gate and her pulse was settling back to normal. But flabbergasted by the experience, Brandt’s boyfriend, Alan Chewning, who had passed security without an incident in another line, fired off a tweet:

“Holy. [Expletive]. TSA @ PHX asked for gf’s passport because her valid DC license deemed invalid b/c ‘DC not a state.’ ”

By the time the two landed, the tweet had gone viral, and stories were flooding in of residents recounting similar horror stories of trying to board a flight with a license from Guam or Puerto Rico.

Asked about the incident, Lisa Farbstein, a TSA spokeswoman, pointed a reporter to the agency’s Web site, which has a published list of 15 types of valid IDs for airline travel, including “Driver’s Licenses or other state photo identity cards issued by Department of Motor Vehicles (or equivalent).”

Brandt did not file a complaint and a person familiar with the matter confirmed that no TSA incident report was filed over the encounter.

Social media exchanges that followed between Chewning and a TSA public affairs officer, however, made clear the agency had been alerted to the incident. In a statement Wednesday, TSA said: “A valid Washington, D.C., driver’s license is an acceptable form of identification at all TSA checkpoints.”

If nothing else, Brandt’s ordeal offered a fresh rallying cry for advocates of D.C. statehood.

Del. Eleanor Holmes Norton (D-D.C.) issued a statement Wednesday saying Brandt’s trouble in Phoenix “dramatically personified” D.C. residents’ lack of voting representation in Congress.

“The rejection of Ashley Brandt’s D.C. driver’s license by TSA because D.C. is not a state has moved collective insult to personal injury,” Holmes Norton said. “The daily disrespect of requiring D.C. residents to pay up on April 15 without a vote in the House or the Senate has now been dramatically personified in the insult to one of our own.”

It was also, perhaps, a lesson on how foreign Washington might seem in Phoenix.

“The whole thing was kind of ridiculous and strange,” Brandt said. “Apparently in Arizona, they’re not sure we’re all right.”