NEW YORK -- Tony Dorson has been coming to the U.S. Open for more than 25 years. He never had to wait so long to get to his seat as he did Monday.

Lines that snaked for a quarter mile or more -- from the exit point of the No. 7 train to the East entrance of the Billie Jean King Tennis Center -- made for delays of up to an hour to get inside the grounds.

All a product of newly installed metal detectors the U.S. Tennis Association is making all ticketholders pass through this year before entering the grounds.

"Never seen it like this," said Dorson, who was on hand for the first session of the two-week event. "People are frustrated. For me, it's worth it, because I love tennis."

The USTA had already limited the size and number of bags fans can bring into the tennis center. It had been considering adding metal detectors even before the Boston Marathon in April, when bombs killed three people near the finish line.

Tournament spokesman Chris Widmaier said the USTA now has what it calls "airport-type security," with the metal detectors and the use of wands to check spectators who set off the detectors. Fans won't need to take off shoes or belts.

Widmaier said fans have voiced their displeasure over the long wait to get in Monday. He said the USTA would continue to ask fans to prepare for delays while also trying to streamline the security process. Gates were scheduled to open a half-hour earlier than usual Tuesday -- 9:30 a.m. EDT -- for matches beginning at 11 a.m. EDT.

"Do I still think it will be somewhat delayed? Yes, I do," Widmaier said. "But given what we saw this morning, we're going to learn from that and make the process more efficient."

The U.S. Open will draw upward of 650,000 fans over the two weeks, many of them watching from 23,000-seat Arthur Ashe Stadium, the largest tennis stadium in the world.

With the lines stretching longer than he'd ever seen, John Sordi took his daughter, Emma, for a walk around the park at Flushing Meadows, then queued up again a little later after the crowd had subsided. It took them about 20 minutes to get in. Sordi said security workers were doing their best to let small children in with less of a wait.

He said the merging of people flowing out of buses, the subway and the Long Island Railroad station, which lets off near the subway, made things confusing toward the back of the lines.

"You weren't really sure where to go," Sordi said. "But we figured it out. It's OK with me. Just need to give yourself a little extra time."