New York: Roberta Vinci was so convinced she would lose to Serena Williams in the US Open semi-finals that she booked a flight out Saturday, never expecting to reach the championship match.

But Vinci’s “magic moment” has forced a major change in plan.

The 32-year-old Italian stunned 21-time Grand Slam champion Williams 2-6, 6-4, 6-4 Friday, dooming the top-ranked defending champion’s dream of completing a calendar Grand Slam and matching the Open Era record with a 22nd career Grand Slam crown.

“I called my travel agency to say, OK, book me a flight, because you know... and then now I have my final tomorrow,” Vinci said. “So it’s incredible.”

Vinci’s astounding upset advanced the world number 43 into an all-Italian women’s final against 26th-ranked Flavia Pennetta, who defeated second-ranked Simona Halep in the other semi-final.

“This is the best match I played in my life,” Vinci said. “It’s amazing. It’s a magic moment for me. You work so hard for a long time. It’s incredible. It’s amazing. It’s like a dream.”

Smiling and exuberant, Vinci spared a moment to ponder the pain Williams must have felt at coming so close to becoming just the fifth player to achieve a calendar-year sweep of Grand Slam titles.

“I’m really happy, but of course I’m a little bit really sad for Serena because she’s an incredible player, number one, almost all the Grand Slams,” Vinci said.

“Almost to complete all Grand Slams. She deserved to win. She’s the number one. So I was a little bit sorry for this because of me she cannot reach the Grand Slam.”

Vinci had never reached a Grand Slam semi-final until this week and now she finds herself one victory from an improbable Slam trophy.

“It’s incredible. I’m 32, almost at the end of my career, and then I make the first US Open final in Grand Slam. I didn’t expect this,” she said.

“I feel good right now. I can maybe touch the sky with my finger.”

Vinci joked she would have to hide her face the next time she saw Williams. “Doesn’t matter if she lost to me today. For me, she’s the very best right now,” Vinci said.

“She’s an incredible player. She won a lot of tournaments, Grand Slam. For me, yeah, she’s the number one.”

But Vinci is the one playing Saturday. Her final match starts seven hours before her ticketed flight departs. “Maybe I can (make it),” she said. “Maybe I can.”