Heighliners

Heighliner visible in the skies of Hagga Basin

Heighliners are starships operated by the Spacing Guild for transportation across the Known Universe.

Lore

More info on Dune Wiki: Heighliner

In-Game

In the game, a heighliner can be seen in the sky at many Locations, such as Hagga Basin and Smuggler's Run. This is presumably the same heighliner we see during the introduction, when the prison transport Proteus arrives above Arrakis.

Spoilers ahead! You feel a compulsion to stay away. Proceed at your own risk.

Other planets

The Arrakeen Spaceport is a way off of the planet Arrakis. A journey takes you offworld to Zanovar. This is presumably the same heighliner used as part of the Journey.