Originally Posted by jchand
You will also get some miles back for the flight( Not sure how meny). ... Just look for the best upgradeble WT+ Fare.
yorweb, welcome to FT!
Just in case you might be confused, all public revenue WT+ fares are upgradeable, so this is not quite as restrictive as it might first sound.
LHR-PHX should be about 5,271 miles + 25% cabin bonus = 6,588 miles each way even without any tier bonuses. So you pays 25,000 miles for the upgrade, but the flight will earn you about half of that back.