XXX-CLT-ORD-PHX-YYY is not usually a "standard" routing and will result in rather high fares.

The multi-city tool from the US website is not the right tool to use to book those multi-segment routings. Kayak/Expedia/etc are better tools.

The reason? US's website, when using multi-city, will price each segment on its own and will try to generate the most revenue! (or so it seems).

This is my approach, I'm sure there are others.

For a 4-segment (each way) itinerary, I'd try to find locations that are served only by one hub (PBG, BHB, FLO, HVN, ISP, etc) and link them together via two hubs (if it's allowed of course).

For instance, I'd search ITA for FLO (only hub: CLT) to ISP (only hub: PHL) by doing this:

Orig: FLO
Connect in: CLT DCA,PIT,BOS,BWI PHL
Dest:ISP
Connect in: PHL DCA,PIT,BOS,BWI CLT

(I specify the mid-way points instead of using "US+" since "US+" is not a mandatory stop).

After you've found it and when you book it, you can specify the following to find the routing when searching on kayak/expedia:

FLO -> (the midway point found in ITA) -> ISP
ISP -> (midway pt) -> FLO

Because the mandatory connection out of FLO is CLT, it will automatically grab it, and the same for ISP's mandatory connection in PHL.

Remember that while the booking engines may limit you to 6 segments, you can still book the fare as two one-way's.

This is of course only one way to do it. I'm sure there are others.

HTSC