Continuing on the theme of online shopping portals, I almost always buy my flights through Travelocity, specifically because of the Ultimate Rewards portal, using my Chase Sapphire Preferred Card.
Chase Sapphire Preferred gives 2 points per dollar spent on travel. You can also use the Ultimate Rewards portal to book travel directly for 3 points per dollar spent on travel. Or you can do even better and use the Ultimate Rewards portal to go to Travelocity, book your travel through Travelocity, and then earn the base Chase Sapphire Preferred bonus of 2 points per dollar spent on travel since Travelocity counts as travel AND get an additional 2 points per dollar spent on Travelocity for going through the Ultimate Rewards portal. Thus, by going through UR to Travelocity, you can get close to 4 points back per dollar spent on flights (It’s not quite 4 points per dollar since you don’t earn bonus points on taxes or fees on Travelocity, but it still usually amounts to more than earning the alternative 3 points per dollar on travel by booking directly through Ultimate Rewards).
To make this even better, you could pay for your flights through Travelocity using an Amex Premier Rewards Gold card which gives 3x points on airfare. Even though you’re booking through Travelocity, the charges are coded as airfare directly from the airlines, so you get the 3x points from Amex as well as the (close to) 2x points from the UR portal. Unfortunately, if the points don’t post, you’ll have a harder time arguing to get them since you didn’t use a Chase card.
This also means that the Chase United MileagePlus Explorer card is largely irrelevant, since it only offers 2 miles per dollar spent on United. Since Ultimate Rewards points can be converted into United miles at a 1:1 ratio, there’s little reason from a points-earning perspective to use the MileagePlus Explorer card over the Chase Sapphire Preferred.