The Texas Giant reaches 14 stories high and has a drop of 79 degrees and a bank of 95 degrees. It can carry up to 24 riders. The ride first opened in 1990 as an all-wooden coaster but underwent a $10 million renovation in 2010 to install steel-hybrid rails before reopening in 2011.
Brown said she was next in line behind the woman and saw her being strapped into her seat next to her son.
"We heard her screaming. We were like, 'Did she just fall?'" Brown said.
Arlington police Sgt. Christopher Cook, the department spokesman, referred all questions to Parker. No other details were available.
In another amusement park accident Friday, a boat on an Ohio thrill ride accidentally rolled backward down a hill and flipped over in water when the ride malfunctioned, injuring all seven people on it. Operators stopped the Shoot the Rapids water ride after the accident, which occurred on the ride's first hill, the Cedar Point amusement park in Sandusky, Ohio, said.
In 1999, a 28-year-old Arkansas woman drowned and 10 other passengers were injured when a raft-like boat on the Roaring Rapids ride at Six Flags overturned in 2 to 3 feet of water about 200 feet from the end of the ride.
Six Flags Over Texas opened in 1961 as the first amusement park in the Six Flags system. It is 17 miles west of downtown Dallas.