- last post: 01.01.0001 12:00 AM PDT
I thought the point was made that after the fall of Reach, the - and this is the important part - entire freaking Covenant fleet followed Pillar of Autumn to the first Halo. After that, they headed straight for Earth. All of them - any remaining outer colonies were ignored.
Similarly, when the Cov. reached Earth they headed for one specific spot - New Mombasa. The Prophet of Regret was looking for something - probbly the location of the master control center (which is probably also the Ark).
My guess - if you're inside the Ark when you set off all the other Halos (releasing the Flood - get it? Ark, Flood?) then you're safe from the Flood. Anything outside is toast. So when the Cov. return to Earth, they probably head straight for the Ark there are probably other humans left on the other continents, ignored just like the other outer colonies, with the Cov assuming the humans will be wiped out as soon as they set off the Halos. Master Chief is probably just the only one in a position to do anything about it. Plus, there's no guarantee the scene Bungie set up as the trailer is exactly part of the storyline, or where in the storyline it comes. That could be toward the end, right before you have to wade into the Ark to stop it from going off.
[Edited on 5/12/2006]