The Duchess of Sussex travelled to the US to watch her friend Serena Williams play in the US Open final.

Meghan is thought to have travelled by commercial plane just weeks after she and husband Prince Harry were criticised for using private jets.

Unfortunately for Meghan and other Serena fans, the US player lost in the final to Canadian teenager Bianca Andreescu.

It was the second straight major final that Williams lost after Wimbledon, with Meghan on that occasion cheering her friend on from the royal box.

The Duke and Duchess of Sussex are among the most high-profile voices calling for action on climate change.

Meghan’s New York trip is thought to be her first since her baby shower in Manhattan earlier this year.

Harry and the couple’s baby Archie are thought to have remained at home in the UK.

Buckingham Palace has declined to comment on the trip.

Williams was trying to win her first Grand Slam since giving birth to her daughter Alexis in September 2017. She was trying to tie Margaret Court’s record 24 slams.

Andreescu, 19, wasn’t even born when Williams won her first US Open in 1999.

The teenager started formidably, breaking Williams’ serve in the first game, and took the first set 6-4.

But Williams saved a championship point in the second set, and came back from 5-1 down to level the Canadian, looking as though she could have taken the final to three sets.

But Andreescu recovered and won the second set 7-5.

Williams and the Duchess have been friends since meeting at an American football Super Bowl party in 2010.

Williams was among a number of celebrities invited to Meghan’s wedding to Harry last year.

(c) Sky News 2019: Meghan watches close friend Serena Williams in US Open final