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Duchess Meghan Markle flew to New York City on a budget commercial airline to watch her bestie, Serena Williams try to win her 24th Grand Slam title in the U.S. Open women's final in Flushing, NY on Saturday.

Meghan was heavily criticized for flying on private jets with her husband Prince Harry after both have expressed environmental concerns in the past.

Williams will take on Canadian teenager Bianca Andreescu, who needed all the tools in her powerful arsenal to defeat Switzerland's Belinda Bencic 7-6 (7-3), 7-5 in Thursday's women's quarterfinals.

Bencic, 22, knocked off the defending U.S. Open women's singles champ Naomi Osaka earlier this week.

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Williams, who is nearing retirement at age 37, easily ousted No. 5-seeded Elina Svitolina of Ukraine in the 1st women's quarterfinals match on Thursday to advance to the final.

"To be in yet another final, it seems, honestly, crazy," said Williams, a six-time U.S. Open champion. "But I don't really expect too much less."

Andreescu makes her first ever appearance in the US Open finals. Thursday's win marked her 12th consecutive victory as she became the first Canadian woman to reach the US Open finals.

The 19-year-old is the odds on favorite going into the finals against Williams.

"I don't think anyone [is] surprised," said Bencic when asked if Andreescu's run to the final was unexpected. "Honestly, she won Indian Wells, Toronto. She beat so many great players. I definitely was not surprised. I don't think anyone should be."

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Meghan and Harry, pictured with American power couple Beyonce and Jay-Z in London, were branded as hypocrites for their costly habit of flying in private jets after claiming to be advocates for the environment and campaigning against climate change.

Meghan and Harry's reps argued that the couple's private jets leave a teeny weeny carbon footprint in the earth's atmosphere. And besides that, they only flew on private jets four times in the past 2 weeks.

The British press reports that Meghan silenced her critics by catching a "last minute flight" on a "commercial airliner" out of London to NYC, but they didn't identify the airline carrier.