A heartbroken Australian woman returning to her adopted American home after burying her grandmother has revealed she was comforted by Prince Harry on a commercial flight from Sydney to Los Angeles on Saturday.

Justine Parkhurst, who was en route to Raleigh-Durham Airport in North Carolina, has spoken of her shock at being suddenly upgraded to the first-class cabin as she boarded her American Airlines flight, and then realising she was seated next to Harry.

Ms Parkhurst shared a picture of herself with the grinning royal, along with a photo showing just how close she was to him as they shared the 15-hour flight to California in a cabin that features seats converting to lay‑flat beds.

Her diagram showed Meghan Markle was seated across the aisle from Harry in a single pod, leaving her husband in a middle‑aisle seat, which meant he was next to a stranger.

Ms Parkhurst said she had just taken her spot on the aircraft and had started crying over the loss of her nanna, whose funeral she had just attended, when she recognised her Harry from across the armrest.

'I sat down and a few tears started to roll down my face, I'm always happy to get the upgrade for that long flight but I wished I had not been on the plane at all,' she posted to Facebook.

'I didn't even notice the person sitting next to me until they were adjusting the seat and getting comfortable. It was Prince Harry.

'His wife was across from him and their security guards right behind them.'

When Ms Parkhurst revealed her grief to Harry, 41, he offered words of comfort.

'We chatted for a minute and I told him that my Nan is the only one I really wanted to tell about sitting next to the royal.

'He said, "She already knows". I believe he is right, I bet she arranged the whole thing.

'We were booked to fly on the Friday but changed our minds and decided to wait one more day and made the change late Thursday night.

'My husband and I got super lucky and were upgraded to first class. While waiting to board, we noticed... two plain-clothed men standing around with guns under their jackets.

'Not alarming, but unusual for sure,' she said.

When contacted for comment, Ms Parkhurst said, 'I will tell you that he was very nice and so was his wife. They were sweet to everyone and each other.'

Harry and Meghan's were flying home after their controversial faux-royal visit to Australia.

Daily Mail exclusively reported that the couple had secretly departed the the InterContinental Coogee Beach Hotel at about 7am on Saturday, after Meghan spent less than two hours at a women's retreat the evening prior, where participants had paid up to $3,200 to spend the weekend with the Duchess. 

Meghan made her appearance for a 'VIP' photo session and a brief Q&A with Her Best Life podcaster Gemma O'Neill on Friday evening, before attending a rugby union match with Prince Harry and her best mate, Soho House exec Markus Anderson. 

By 8am the following morning, a small motorcade which included NSW police protection deposited Meghan and Harry at Sydney International Airport through a side gate, where they boarded the American Airlines twin-jet Boeing 777-300ER ahead of its 9.10am departure.    

For a couple who have copped flak over their use of gas-guzzling private jets over recent years, the Duke and Duchess appeared keen to avoid any environmental or cost-of-living controversy on their tour, as Australia grapples with a fuel crisis due to war in the Middle East.

Given they are used to travelling in the lap of luxury - often on planes supplied by their billionaire friends - their choice to fly on American Airlines raised eyebrows. 

The airline is rarely mentioned in the same breath as other first-class offerings, such as Qantas, which flies the same route but did not depart until Saturday evening.  

Indeed, AA does not even feature in the top-five list of first-class cabins operating into Australia by flying bible Points Hack, which describes it as feeling 'largely like a very good Business Class, rather than truly First Class'.

Still, it was an upgrade from the couple's inbound flight from Los Angeles to Melbourne on April 14, on day one of their tour, when they flew business class on Qantas flight 94.

That aircraft - a Boeing 787 Dreamliner - did not feature a first-class cabin.

The couple also flew Qantas on a domestic flight between their Melbourne and Sydney stops.

When Harry made a brief detour to Canberra on Wednesday, he flew Qantas with a small entourage. 

Meghan and Harry are said to have concluded their tour - which included the women's retreat, a sail on Sydney Harbour, and visits to a children's hospital, the Australian War Memorial, and a veterans' art museum - was a major success.

Meghan even appeared on MasterChef as a judge, in an episode that will be aired later this year.  

But a poll of Australians has given a brutal verdict of their four-day visit, with the majority - 81 per cent - declaring that it did not improve their view of the couple at all.