A fake bomb strapped to girl's chest was the reason for her arrest at Logan International Airport.
Star Simpson, 19, had a computer circuit board and wiring in plain view over a black hooded sweat shirt she was wearing, said State Police Maj. Scott Pare, the commanding officer at the airport.
Simpson was "extremely lucky she followed the instructions or deadly force would have been used," Pare said. "She's lucky to be in a cell as opposed to the morgue."
The device had wires connected to a battery, allowing it to light up, he said. Simpson also had Play-Doh in her hands.
The phrases "Socket to me" and "Course VI" were written on the back of the sweat shirt, which authorities displayed to the media. Course VI appears to be a reference to MIT's major of electrical engineering and computer science.
"She said that it was a piece of art and she wanted to stand out on career day," Pare said at a news conference. "She claims that it was just art, and that she was proud of the art and she wanted to display it."
Simpson was charged with disturbing the peace and possessing a hoax device, and was to be arraigned later Friday.
Pare said the incident is a reminder of the terrorism threat confronting the civil aviation system. Two of the four passenger jets hijacked on Sept. 11, 2001, took off from Logan.
"In this day and age, the threat continues to be there," said Pare. "She certainly jeopardized her own safety by bringing this to the airport, as well as the safety of everybody around her."
Simpson is a Massachusetts Institute of Technology sophomore from Hawaii, officials said. MIT spokeswoman Patti Richards said aside from confirming she was a student, the school did not have any comment.
She was arrested about 8 a.m. outside Terminal C, home to United Airlines, Jet Blue and other carriers.
A Massachusetts Port Authority staffer manning an information booth in the terminal became suspicious when Simpson - wearing the device - approached to ask about an incoming flight, Pare said. Simpson then walked outside, and the information booth attendant notified a nearby trooper.
The trooper, joined by others with submachine guns, confronted her at a traffic island in front of the terminal.
Pare said Simpson took a subway to the airport, but he was not sure if she had the device on at that time.
She told authorities she was at the airport to greet someone arriving on a flight from Oakland, California. Authorities verified the name of the passenger and said he had already left the airport.
"She did seem a bit upset that she was in custody. However, she was rational, and she did answer all questions as required," Pare said.
Boston was the focus of a major security scare Jan. 31 when dozens of battery-powered devices were discovered in various locations. Bomb squads were deployed, and highways, bridges and some transit stations were temporarily closed. They turned out to be a promotion for cable TV's Cartoon Network.