Forgive a newbie to this board, but . . .

I was pricing SLC-HNL first class over the 4th of July. Cheapest was US Air @$1363 - thru DEN. Then I noticed that the entire flight was on UA metal or UA Skywest. I priced the same itinerary on UA site for $3403.

Does this mean I could buy the US Air pricing, but then get UA miles for the trip? or is there some catch to all of this.

Flights are:
UA 6608-43-42-1122
US Air 7638-6097-6098-6007

I did a search but this didn't pop up. I'm always cautious when something looks to good to be true.