Locations are connected to the grid if you can trace a line from them to the starting havens. The Shuttle Flight action allows you to move from a haven or supply center to another haven or supply center on the grid.
Is a haven that has not yet been accessed, but has a sea lane to it (from another city on the grid) , a valid destination for the Shuttle Flight? Technically it is a haven connected to the grid, but RP-wise it seems like we shouldn't be able to shuttle to it.
Normally I'd leave this as a comment since it doesn't cite any official source, but it's answer-y enough and comments don't have spoiler tags.
As you say, the plain text of the rules would seem to say this is allowed. And I think it does make sense RP-wise as well: "accessing" a haven basically means searching it (for tools, notes, inhabitants, etc), but in order to fly somewhere you just need to know where it is (it's on your map) and how to get there safely (you've charted a sea lane to it). The only problem RP-wise is if there's nowhere to land safely - you know havens have landing strips but you could argue it might be in sufficient disrepair that you can't use it, and that part of "accessing" a haven includes fixing up the strip.
From the rule book:
THE GRID
The board is largely empty as the world is mostly unknown to you. “The grid” refers to any location that is connected to the starting havens (i.e., a path can be traced along supply lines and/or sea lanes to the starting havens).
EXPANDING THE GRID
As you explore the world, you will expand the grid. Whenever you open a sticker that expands the world map, add that sticker to the board, aligning it using the latitude and longitude lines.
Therefore, if you add a sticker to a board, you are expanding the grid. Any connections on those stickers are connections to the grid (provided there is an unbroken path back to the starting havens)
For the haven off the coast of South America, it connects to Lima by default. As long as you've connected Lima to the rest of your grid, you're good to shuttle flight to it. You've not "accessed" the haven until someone goes there!
Thematically,
it makes sense you can access it via shuttle flight, as it's a platform out in the ocean - so the way you can access it by air is a helicopter (which is flexible in where you disembark, it doesn't have to land for you to leave it, just be close enough to the ground, hovering. The other option would be from a seaplane, in which case you'd be accessing the platform much the same way as you would via a boat.
The image on the action has arrows going between a supply center and a haven, so I agree you can do it.
