Melbourne, Australia - Kim Clijsters moved into an Australian Open semifinal showdown with second-ranked Vera Zvonareva, beating Agnieszka Radwanska 6-3, 7-6 (4) on Wednesday as air force planes flew in formation overhead as part of celebrations for the national holiday.

Cannons went off earlier when Zvonareva started the Australia Day proceedings at Rod Laver Arena with a 6-2, 6-4 win over Petra Kvitova.

Thursday's semifinal will be a rematch of the last U.S. Open final, where Clijsters collected her third Grand Slam title.

Clijsters is the only Grand Slam winner into the women's semis, although she's still seeking her first major title outside of America. No. 1-ranked Caroline Wozniacki and China's Li Na meet in the other half of the draw.

"I hope the experience can help me a little bit," Clijsters said. "But there are some tough players out there, we have Nos. 1, 2, 3 still in and Li Na has been playing really well. So it is going to be really tough.

"I lost to Vera at Wimbledon last year, I beat her in finals of U.S. Open."

Zvonareva has lost the last two Grand Slam finals, to Clijsters in New York and Serena Williams at Wimbledon.

Clijsters was up a set and a break before Radwanska rallied, winning three straight games to lead 5-4 with a chance to serve for the second set.

With six Royal Australian Air Force "Roulettes" flying overhead, Clijsters converted her fourth break-point chance to tie it at 5 and the set went to a tiebreaker.

"I think the planes kind of took me up higher!" joked Clijsters, long a crowd favorite in Australia, where she's still called "Aussie Kim." She also was engaged for a time to former No. 1-ranked Lleyton Hewitt.

"Happy Australia Day everybody," she said in a salute to her supporters.

Clijsters now has reached the semifinals five times in Australia. Her best run remains her trip to the final in 2004, when she lost to fellow Belgian Justine Henin.

Zvonareva wore a black ribbon on her hat in honor of the 35 victims of the suicide bombing at a Moscow airport this week. Her quarterfinal also featured a couple distractions.

Zvonareva and Kvitova were surprised when cannons went off in a nearby park. And Zvonareva asked that the match be stopped for a few minutes while a woman in her sightline was given medical attention in the stands, but chair umpire Mariana Alves told them to continue.

"I didn't know they were going to start this noise during our match, it was a difficult moment," said Zvonareva, who led the final set 3-0 before the disruptions but saw Kvitova level it at 4-4. "You're here to play tennis ... I was trying to keep my concentration."

On Tuesday, Roger Federer was reluctant to talk about possibly playing Rafael Nadal in the Australian Open final, and with good reason.

After all, he's playing Novak Djokovic in the semifinals.

Federer and Nadal have dominated the Grand Slam tournaments, winning 21 of the last 23 titles. But Djokovic is dangerous, and Federer knows his one-match-at-a-time mantra is sound strategy.

"He takes it to the opponent," Federer said.

Federer routed Stanislas Wawrinka 6-1, 6-3, 6-3 in the first all-Swiss quarterfinal at a major. Djokovic eliminated Wimbledon finalist Tomas Berdych 6-1, 7-6 (5), 6-1 on Tuesday night.