Thanks for the replies, Clouds and Rory.
IMHO it's going to be totally RESISTED by flat-earthers every which way, to the point where any mention of the flight (after it's been completed) will be denounced unequivocally as a fake project. Satellite data showing tracking of the plane like by NORAD or GPS will be rejected as conspiracy nonsense. Some might revert to denying the existence of satellites (such as "because of the dome"), or that GPS is operated by way of the cell phone tower network, or that NORAD is just as fictional as NASA's photos.
Flat-earthers await their esteemed leadership to come out with the "party line" to which devout lemming followers all adhere, without thinking on their own. Therefore any consequential discussion must take place with such leaders, but keeping them accountable and honest is a big problem. None of them are going to give assent to questioning, any more than any of them are eager to step up to the plate by occupying a free seat on the plane.
Nonetheless, I hope the flight takes place as planned, and I hope there are scads of documentation, eyewitnesses, corroborating checkpoints, video footage, interview testimonies and physical evidence. It would be helpful if some passengers who embark on the first leg disembark at subsequent fuel stops, and other passengers embark to take their places. In that way, those who did not take the full round trip can be interviewed on location after disembarking at the various fuel stop locations amidst easily-identified surroundings, with which they are seen interacting so as to show that it's not a blue screen backdrop. I might be expecting too much, though.
Come to think of it, there are polar-orbiting satellites, that is, satellites that orbit the earth north-to-south such that they pass over the arctic region and the antarctic region alternatively. USA spy satellites passing over Russia (alias USSR) have mapped out scans along meridian lines all across Asia. I've seen flat-earthers try to deny that such a thing is possible. Some have gone from ambivalently accepting the principle of satellites to rejecting them entirely after having been faced with these north-south orbits, which are highly problematic against the flat-earthism fantasy world.
I recall seeing a cute explanation that tried to apply a "PacMan" scenario such that a satellite or aircraft that passes over the antarctic disappears on that side of the "flat" earth only to reappear on the diametrically opposite side, like PacMan could disappear on the left side of the screen only to reappear on the right side.