Continental Airlines Inc. said it will eliminate 600 additional reservation-agent jobs, about 23 percent of its total, as more travelers book their own flights.

The reductions are the second in less than a year among its workers who help passengers arrange trips by telephone. The airline in May said it would trim 500 such jobs and shut a Tampa, Florida, call center. The latest cuts take effect April 11, Continental said in a companywide bulletin today.

Continental, the fourth-largest U.S. airline, today blamed a 15 percent drop in call volume, as technology improves and customers increasingly use the Internet for purchases. The Houston-bases carrier also isn’t renewing a contract to take customer calls for Walt Disney Co., affecting about 100 workers.

“Customers prefer to book and manage their flights at Continental.com, and that’s reduced the number of calls coming into our call centers,” Julie King, a spokeswoman for the carrier, said in an interview.

Continental charges $20 to make a reservation by phone.

The positions will be cut from the carrier’s call centers in Salt Lake City and Houston, and from about 1,000 agents who work from home. About 250 of those who will lose jobs already are on leave, King said. Continental will have about 2,000 of the workers after the reductions.

The airline didn’t renew the Disney contract because the costs of wages and benefits for those workers exceeded revenue from the agreement, Martin Hand, Continental’s vice president of reservations and e-commerce, said in the e-mail bulletin.

“We must recognize the reality of today’s market and reduce the size of our reservations workforce accordingly,” Hand said.

The airline will offer an early-out program to agents who have worked for Continental 10 years as of April 11, as well as severance and job-hunting aid for those losing their positions.