742Dash

There are many ways to approach this, from incredibly light to packing like the queen on a long holiday. But I think that the most common approach is to pack for 7 days. You can do laundry on the road, but you do want to plan ahead and not run yourself down to zero clean clothes because of schedule changes.

There is also a thing called "travel clothing", which is similar to some hiking stuff. Light weight, sink launder-able, dries overnight. I usually buy it from REI. Along the same lines one or two sets of ExOfficio underwear in the mix with your normal underwear can really extend the time between real laundries. Look up Merino wool socks.

Laundry detergent is made in sheets, which packs much better than the powdered stuff. You can find it on Amazon. Also on Amazon are disposable/emergency rain ponchos for $1-$2 each. I carry two of them during the warm weather for preflights in the rain. But if you are on the 74 keep in mind that you are just one schedule change from being on the other side of the equator, so don't get too confident about the temperature range that you are packing for.

You don't need as many uniform shirts as you would think, especially if you don't make a habit of doing the passenger flying. Embrace the freight dog that is in all of us. I pack 2, occasionally 3.

Be ruthless and don't let yourself fall into the trap of over packing. It is surprising how little you actually need.

Personally I use a barely legal carry-on sized bag, but I do check it. A pair of spare underwear and socks in my actual carry-on/flight bag "just in case" and that is that. I can count on one finger the number of times that I have jumpseated on a passenger airline, and I have been here for a long time.

LPT. If you do check a bag turn your PCD OFF and keep it OFF until you have your bag in hand at the destination. Do not be that guy in the airport with a checked bag who is looking at a schedule change. Let that be scheduling's problem until you have all your stuff back in hand.

YMMV.