Harry & Meghan Arrive in NYC, Diana's Ex-Butler Says They Should Lose Titles

Prince Harry and Meghan Markle seem to be in strictly business mode ahead of their controversial Netflix doc's premiere -- a project that has a former friend of the family saying they should lose any trace of royalty they have left.

The Duke and Duchess of Sussex landed in NYC Monday, where they stepped off their private jet shoulder-to-shoulder and met with a group of friends on the tarmac before they were on to their next destination.

The trip comes directly on the heels of the latest trailer for "Harry & Meghan" -- in which they appear to take a scorched-earth approach toward his family while describing their experience trying to bring MM into the royal fold.

Harry's got a pretty serious face on here, as does Meghan -- who's wearing shades, but flashing the slightest of smirks too. No doubt, they've heard the waves of criticism for the documentary ... particularly across the pond, as they say.

Princess Diana's ex-butler, Paul Burrell, turned on his late boss's son publicly Monday night as he told Piers Morgan ... Harry and Meghan should be stripped of their remaining Royal titles.

Speaking out on the UK's Talk TV, he said Diana would be horrified by Harry's approach to disconnecting himself from the monarchy -- even if she could, in principle, support his move to America.

Burrell claims she would not have approved of what he describes as a route laced with "commercialism."

Burrell says the Duke and Duchess crossed a line, just from what he's seen in the trailer ... and he believes the actual series will be even worse.

He says King Charles should take a stand and turn them into true Average Joes.