As heavily armed law enforcement officers and bomb sniffing dogs patrolled the sprawling Billie Jean King Tennis Center, a packed Arthur Ashe Stadium with 9/11/01 stenciled into the court observed a moment of silence followed by a flyover of four F-15E Strike Eagles.

The U.S. Open’s Flushing Meadows home is just 10 miles to the northeast of the site of the former Twin Towers of the World Trade Center, the 2001 attacks left a mark on the sprawling facility and many players.

At the Open in 2001, a 20-year old Australian Lleyton Hewitt defeated American Pete Sampras to win the men’s final two days before the attack.

Several of the players in that year’s tournament left New York on flights in the days and even hours before the Twin Towers came down.

Over the years since, scores of top tennis players from around the world have made their way to the site of the Twin Towers. Spain’s twice U.S. Open champion Rafa Nadal, who was 15-years-old in 2001, has said he has gone to memorialize the 9/11 victims at least a half dozen times over the years. Serb Novak Djokovic, who played Swiss Stan Wawrinka in Sunday’s final, in 2009 invited several children of 9/11 victims to see him play at the Open. American Bethanie Mattek-Sands, who began Sunday’s action on Arthur Ashe Stadium court partnering with Lucie Safarova, paid her own tribute wearing Stars and Stripes knee-high socks and wrist bands.

“It is an emotional day,” said Mattek-Sands, who won gold at the Rio Olympics in mixed doubles with Jack Sock. “I was going to retire my American flag socks after the gold medal match.

“I said, You know what? For the final of the U.S. Open, 9/11, have to bring them out.

“It was really special for me to win it here today in New York.”

In Lower Manhattan on Sunday morning, thousands gathered at the 9/11 memorial site to commemorate the 15th anniversary, as police, firefighters and rescue workers mixed with victims’ families and U.S. presidential candidates Hillary Clinton and Donald Trump. Clinton left the ceremony early after feeling unwell on a hot, humid day.

Even Roger Federer, the seven-time champion and a lifelong admirer of the All England Club’s traditions, has ramped up his criticism of the rule which demands predominantly white outfits.

“I love Wimbledon but they’ve gone too far now. The rules have become ridiculously strict,” said the Swiss legend.

It is the second time in two seasons that Federer has hit out at the rule which calls for “suitable tennis attire that is almost entirely white”.

“We’re all white. White, white, full-on white. I think it’s very strict,” Federer said 12 months ago.

“My personal opinion, I think it’s too strict. If you look at the pictures of Edberg, Becker, there was some colours, you know, but it was ‘all white’.”

The colour code at Wimbledon is often controversial.

Last year Caroline Wozniacki said reports that officials would check the colour of women’s underwear as “a little creepy”.

This week, Canadian poster girl Eugenie Bouchard fell foul of the rules after wearing a black bra.

Flamboyant American player Bethanie Mattek-Sands said she supported Federer’s complaints.

“I didn’t even get married in white,” she said.

Mattek-Sands once appeared on Wimbledon Centre Court wearing a coat made of tennis balls and has also taken to a court with warpaint beneath her eyes.

She claims a Nike-designed white playing bra was judged to be unsuitable at Wimbledon because it had a yellow stripe.

“I think it’s gotten a little excessive. It was funny, because I was actually Googling some players like when John McEnroe played, Arthur Ashe, they had colour everywhere,” said Mattek-Sands who makes a mini-statement by appearing on court with knee-high white socks.

“I feel it’s actually gotten stricter. You can’t even wear off-white or cream. I was like, man, if you wash your whites too many times, they will be illegal. Better be washing it in cold water.

“I had a little mesh on my shirt today (in Wednesday’s win over Ana Ivanovic). I have like I think one legal pair of shorts that is on rotation hopefully in cold water. One skirt I think that’s legal.”

Mattek-Sands, 30, would never be one to settle for the ordinary when it comes to fashion choice.

When she married insurance executive Justin Sands in 2008, she walked down the aisle in black.

“I actually wore a black dress. When I went shopping for it, they wanted me to try some stuff on, and I said, Look, I’m not going to wear anything white, off-white, cream, light pink, I said, so just don’t even hand me those,” she recalled.

“They’re like, Well, we have this black evening gown. I’m like, Perfect. First one I tried and got that one.”

On Thursday, Wozniacki said, like it or not, players have to accept the rules.

“If they say it’s all white, it’s all white. You try and be creative,” said the Dane after reaching the third round.

“We’ve tried to do that with my dress. But I think every tennis player enjoys to play with a tiny bit of colour. It’s fun to try to be creative even though you have to wear white.”