Before booking anyting I highly suggest looking at both UA and CO .coms and do so as 1 ways its $79 PHL-LAS with the tx = $100.40
I second that. When booking an itin to PHX from the East Coast on UA as part of a RT, it was only letting me choose from CLT, ORD, DEN, and IAH for layovers.
However, when booking the outbound and return trips as separate itineraries, it also gives me SFO as a choice -- very nice for EQMs.
EDIT: After messing around with the UA and CO sites I was able to get CO to give me three segments on the eastbound return, including a redeye SFO-ORD on a 767, which gives me good odds for an upgrade.
for a Segment Elite it may pay to grab as many Segs as they can, but all too often I find that by throwing in an extra seg (when Im a Miles person) that the final amount of miles isnt that much more < 500 and can mean having to waste a few hours over say a 1 stopper or a non-stop eg IAD-LAS is <100 miles then IAD-DEN-LAS yet it saves a few hours of traveling, so as long as the IAD-LAS flight has the cheap fare and the seats I want, then I wont waste my time going via DEN
for me to justify an extra stop either it has to be due to being able to get a much cheaper fare or close to an extra 500.
Thats why when heading to the LA area from NY I will fly JFK-SFO-XYZ, since the non-stop is 2475 miles and via SFO its 3086 or +1222 on the r/t