All right, I rewatched entire Starfield demo and I'm 90% sure the game doesn't allow manual planetary landings. Unless the demo didn't include them, or unless manual landing gameplay mechanics is not implemented in game yet.
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Starting at 5:37, we can the
Navigation Console onboard our demo starter ship (pic 1 below)
Todd Howard says: "this is your Star Map (...) You can choose a landing spot or fast travel to known locations".
There is a
SET LANDING TARGET (A) on the Star Map UI.
LAND (X) appears when Howard stops the map spinning somehow -- then we can select landing spot in the middle of the forest (pic 2), or move the landing target to the nearest outpost (pic 3).
The same (X) button is then used to send the ship to The New Atlantis. The next scene we can see is a landing. It clearly looks like an automated landing (animation), the same as all other landings which can be seen in Bethesda demo. It is the same sequence in all cases: a view from below, then from the cockpit, from rear, followed by the overhead view (pics 4-5).
I'm afraid takeoff is also automated, even from the middle of the planet or a moon. Again, it looks like the same sequence, no matter if we are leaving a moon (pic 6) or a planetary landing site (pic 7).
The reason why Starfield (probably) works like that is obvious: map switching. I guess all those planets and moons which can be seen in the sky or in Star Map are simple 3D objects only. Once we click (X), the game loads a new map and spawns our ship in it. The same happens when we leave the planet or a moon; I guess this time the game loads a single Star Map map with all 100 star systems, including 15 known ones like Alpha Centauri or Sol.
Don't get me wrong -- I still think it would be a cool game. I can't wait to play it (once all day 1 major bugs are fixed ; )
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Pic 1
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Pic 2
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Pic 3
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Pic 4
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Pic 5
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Pic 6
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Pic 7
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For reference: