The device had wires connected to a battery, allowing it to light up, he said. Simpson also had Play-Doh in her hands, he said.

Simpson was charged with disturbing the peace and possessing a hoax device, and was to be arraigned in East Boston District Court later today.

"I'm shocked and appalled that somebody would wear this type of device to an airport," Pare said.

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."

Simpson is a Massachusetts Institute of Technology sophomore from Hawaii, officials said. A spokeswoman for MIT had no immediate 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 was allegedly picking somebody up," said Pare.

The major praised the booth attendant but 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."