Delta reviewing how a man who followed a family onto an aircraft boarded the wrong plane

A Georgia mother is demanding answers from Delta Air Lines after an alarming incident on her family’s flight earlier this month.

The airline is investigating what led to a man boarding the wrong plane at Washington Dulles International Airport earlier this month.

Lauren Benton told ABC News that she, her husband, and their 9 and 6-year-old children were flying home from Dulles when she noticed a man who appeared to be following her family throughout the terminal.

"My heart started beating immediately -- I didn't know what this man's intentions were," Benton told ABC News. "He was standing in the ladies room washing his hands, and I was immediately alarmed."

Benton said she tried to keep her distance, but when the family boarded the plane, that same man boarded as well and sat down right in their row.

"My husband assertively confronts him and says, 'Hey, is this really your seat?' And the man says, 'yes, it's my seat,'" Benton recalled. "The stewardess requested to see the man's boarding pass -- he was unable to produce it."

The unidentified passenger was then escorted off the plane and according to the Transportation Security Administration, there was no security violation since he had a valid ID and boarding pass for a different flight that day.

Gerry Phelan, a former federal security director at several airports, told ABC News that "Delta should ensure that that boarding pass matched up with the individual, which it did. But it certainly didn't match up with the flight that they're boarding that time."

In a statement to ABC News, the Atlanta-based carrier said: “Delta has processes in place for gate agents and flight crews to verify that individuals onboard aircraft prior to departure are customers that are booked on that particular flight. Delta is reviewing the matter in question internally and has been in touch with airport authorities in conjunction with this review."

A representative for the Metropolitan Washington Airports Association also confirmed to ABC that police who were called to the departing gate spoke with the man, but no charges were filed.

"The passenger exited the aircraft and returned to the terminal to continue their journey," the officials said.

Benton said her children felt traumatized by the incident and she's now warning other travelers to remain vigilant.

"Pay attention to your surroundings and follow your gut instincts," she said.