Well Fassbender is a Fantastic Actor.
This does not have to mean David though, it could be Walter, who knows its either David or Walter thats for sure... and yes Chris it could be the scene Waterston mentioned the other day but then there could be a number of scenes running away.
Comments are starting to paint a picture now, depends if every one who was made comments (Ridley, Production and Cast) are describing the same movie and not previous incarnations or ideas.
Here is the Picture thats painted.
*Covenant and Crew Arrive at Paradise they expect to find a World that is i ideal habitat to start a fresh life and colonize.
*They however at some point find David 8 from Prometheus as the only inhabitant of Paradise, which seems a surprise to most of them.
*The Covenant has its own more advanced Android David called Walter who is a bit distrusting with David 8 and concerned over how he has gone so long with out maintenance.
*David 8 is a character with a creepy but persausive personality.
*The Covenant crew arrive and find a scene of disaster.
*And there is a Evolving Creature that the Engineers (or their Black Goo) created.
*All Hell breaks Loose, and we see Multiple Chest Buster Events (or similar) we see all stages of the Xenomorph (or similar Organism).
*Crew are being killed off few at a time.
*some survivors attempt to make a Harrowing Escape.
*These Survivors which at this point include at least Waterston, McBride and Ejogo as they are chased on board a Ship by Aliens.
*Some point either David/Walter join Waterston in being chased.
*Waterston and Ejogo are chased while in a Space Suit by Large Aliens.
*Wayne Haag confirmed the movie is set on Paradise and a Ship, they crew arrive and land, and then attempt escape back on the ship.
*Janty Yates says the movie is not a Space Suit Movie (which means the Crew dont need Suits for the most part), as Paradise is Habitable and The Covenant has Life Support. she also said the suits are more similar to Alien ones apart from David 8 who would be in the Prometheus style (we have to assume Shaw too).
so it paints a good picture, where it appears the Crew Land, find eventually David, something related to the Xeno gets out or infects some of the crew... they get picked off and survivors try to escape in A Ship, we have to assume Covenant.
But Aliens get onboard that, and at some point despite the Ship having Life Support (Covenant) and Paradise being Habitable they would need Space Suits.
To me this means
1) The Atmosphere on Paradise is compromised, related to Black Goo contamination or Spores etc.
2) They are on the Covenant main Ship and its Life Support is Compromised (Shooting Xeno related Organisms with Guns is not safe)
3) Do they get onto a Engineer Ship with no Life Support once its in Space?