An enigma on United Flight 923, Catherine Mayo was a mystery in her small Vermont town, too. The 59-year-old caused a security scare when she passed notes to crew members, urinated on the floor and made comments the crew believed were references to Al Qaeda and the Sept. 11 attacks on the London-to-Washington, D.C., flight, according to an affidavit.

The petite woman, wearing a Rolling Stones T-shirt, black pants and white socks without shoes, appeared in federal court Thursday on a charge of interfering with a flight crew that could land her behind bars for up to 20 years. She was ordered held pending a detention and probable cause hearing next week.

Her arrest brought attention to this town of about 1,200 in central Vermont, where Mayo was largely unknown.

"To hear our little town of Braintree on the national news was a little bit spooky this morning, but it doesn't seem to be anyone we're familiar with," said Town Clerk Linda Michalec.

Mayo rents a modest, gray former schoolhouse surrounded by horse pastures but spends months overseas. The front door was padlocked Thursday. Nearby was a neat stack of firewood and bound perennial flowers in the front yard.

Someone who answered her telephone said she was out of the country. The man who rents the house to her said she pays a year in advance.

Mayo's son, Josh, 31, described his mother as a peace activist and said she had been in Pakistan since March. She has traveled there often since making a pen pal before Sept. 11, 2001. The pen pal hasn't been allowed to visit the United States, he said.

"I guess she just had a bit of a bad time on the plane and everybody's a little paranoid," he said.

Henry Lefebvre, a neighbor who met Mayo a couple of years ago at a picnic, said she told him she was headed to Pakistan.

"She said she had a boyfriend there," he said.

When she first visited Pakistan, she sent letters home in which she sounded like a tourist and, later, ones that didn't make sense, said Kevin Hall, who rents to her.

In a rambling 2003 column for the Daily Times of Pakistan entitled "An American in Pakistan: A new kind of arrogance," Mayo criticized the United States. She wrote: "Once America decided that might is right, everything else became a cliche, too. When dissent is not allowed, all truth becomes predictable."

The scare aboard United 923 came just a week after London authorities said they foiled a terror plot to blow up trans-Atlantic flights. As many as 17 people have been arrested in Pakistan in connection with the London terror plot, but federal officials have said they have no indications that Mayo had any links to terrorism.

United 923, with 182 passengers and 12 crew members, was diverted to Boston and landed safely — with two fighter jets escorting it — after the pilot declared an emergency on board. Crew members said Mayo spoke of being in Pakistan and made remarks the crew believed were references to building a bomb.

FBI spokeswoman Gail Marcinkiewicz confirmed that authorities found a screwdriver and an unspecified number of cigarette lighters in her bag, items which are banned under new security regulations. Marcinkiewicz also confirmed that matches were found in Mayo's bag.

Her attorney said Mayo was "just barely lucid" when they spoke.

"She's got some very serious mental health problems," said federal public defender Page Kelley.