SEOUL (Reuters) - Financial markets stayed closed and aircraft grounded as students in South Korea sat down on Thursday morning for the annual college entrance exam that could make or break their careers.

Some 600,000 high school students will take the grueling eight-hour exam to determine if and where they will spend four years in higher education, with anxious parents heading to places of worship to pray for their children.

The students, including those retaking the exam, were overwhelmed with well-wishes and gifts of sticky rice cake, said to bring good luck.

"My little boy is taking the exam for the third time," said Kim Yong-woo, a 59-year-old mother, who joined other parents at cathedral to pray for their children.

"All I can do is pray as his mom and I came out here hoping that he can manage his condition well and get a good score he wants," she said.

The November event, which includes mathematics, sciences and languages tests, sees the country ground to a halt each year.

For 25 minutes, when the listening portion of the English test is administered, the takeoff and landing of aircraft are put on hold and bus drivers traveling near test sites are discouraged from sounding their horns.

Police vehicles and motorcycles were enlisted to escort students running late to the exam.

Financial markets opened an hour later and office workers were advised to be at work later than usual to allow students to get to the exam venue in smoother traffic.

At test sites, students arrived with mixed feelings of concern and anticipation of liberation when the exam is behind them.

"I won't get nervous and I will work hard to solve problems in exams as I've been preparing," said Lee Se-la, 19, steeling herself for the day-long test.

(Reporting by Hanbin Yoo and Sang-gyu Lim; Writing by Ju-min Park; Editing by Patrick Johnston and Simon Cameron-Moore)