NEW YORK -- A fan's head turns with each whack of the ball at the U.S. Open. Jet engines roar, building in volume. The match is ignored as the fan scans the sky. The plane turns and only then do the fan's eyes return to the court.

Planes are usually rerouted so as not to fly directly over the National Tennis Center, but with memories of Sept. 11 still fresh, the air traffic seemed too close to some onlookers Monday. Only 500 paces from Arthur Ashe stadium, where New York police officers were stationed, one officer remarked, "You just hope the planes don't turn right," watching as an optical illusion made a plane seemingly pierce through the Unisphere.

As the sound of the blimp, helicopters and airplanes hummed, rattled and boomed overhead, tennis coach Terry London occasionally took his eyes off a practicing Thomas Blake and focused on the horizon. For most tennis players, a bad injury or loss forces them to consider retirement. For London, 31, his fear of flying led to the end of his playing career and now -- thanks to the events of Sept. 11 -- tennis altogether.

Last year, the sound the planes made was merely an annoyance.

"Before (Sept. 11), people really didn't pay attention to the planes because it wasn't worth missing a point," said renowned tennis coach Nick Bolletieri. "Now I think looking up is just more of a natural reaction."

On the upper level of Louis Armstrong Stadium, the planes were close enough so that fans -- including Mary Kay Ackerman -- could clearly see the airline's name on each plane that came into view every two minutes or so.

"Seeing all the planes definitely gets me nervous," said Ackerman, a surgical nurse from Pittston, Pa., attending her second U.S. Open. "Because there's such a crowd here, because of what happened and because it's an international event."

"I think everyone in New York, no matter where they are, looks at the sky more than they did before when they hear a plane," said Leonard de Montagnac, a 32-year-old tennis fan from New Jersey. "I don't know if we'll ever get over that."

Despite reminders of the events, like the 2,700-pound bronze statue of a kneeling firefighter on loan and the tattered American flag from the World Trade Center being raised, some were not concerned. "I'm not really worried about the planes anymore," 16-year-old Matt Golob from Long Island said.

None of the players who were asked -- Albert Costa, Ashley Harkleroad, Jan Vacek, Magnus Norman or Alex Bogomolov Jr. -- said they were more affected than usual by the planes.

But London, who plans to become a real estate broker, even has trouble looking at planes these days. He used to log 100,000 miles a year traveling from event to event, something he hasn't done in an airplane since last August.

"I couldn't play because I got so worked up on planes," London said. "Now I can't even fly to coach."

Darren Rovell can be reached at darren.rovell@espnpub.com.