Let's suppose that one wants to fly LAX-IAD-LHR rather than LAX-LHR either to have dinner in DC or just for the added FF miles, but that the IAD stop puts one over MPM. One could book a direct flight that connects in IAD e.g. UA924 in the present schedule. Then one could separately make a full fare reservation in the appropriate class of service on an LAX-IAD nonstop which leaves before the LAX-IAD-LHR leaves. One could go to the airport early, check in for LAX-IAD-LHR as ticketed on the RTW getting separate boarding passes for the two segments because you prefer aisle on one and window on the other, then proceed to the gate from which departs the earlier flight. Present only your LAX-IAD boarding pass, tell the agent your travel agent made a reservation on the earlier flight in case you arrived early at the airport, and ask if you can get on the earlier flight.

I don't think there are a lot of cases where this is possible, but it should work in some cases. I haven't actually tried this, but I think it should work. Has anyone tried?

I'm confused...maybe you need to go slower.

If LAX-IAD-LHR puts you over the MPM, then you would you get it ticketed (or are you suggesting that you don't stop over in this ticket?)

If you are suggesting you don't stop over and you actually fly on the full fare that you've bought, what's the point? And will you not have to get your original itinerary reissued because you've missed one segment?

I'm suggesting that one could ticket it LAX-LHR (not LAX-IAD-LHR) on a direct flight (for example UA924). Normally, if so ticketed, the nonstop LAX-LHR mileage is counted toward TPM (against MPM) and FF miles are awarded only for the nonstop mileage.

I'm not suggesting buying/ticketing the full fare reservation (LAX-IAD). I suggest one could make said reservation and leave it unticketed to ensure that the seat will be available when one shows up (with boarding passes already in hand for the ticketed later flight) to the gate from which departs the earlier (unticketed reservation) flight.

Interesting to think outside of the box, but not a great plan. What would work would be to check in for the original flight (with two boarding cards/ different seats), and then go standby for the earlier one.

Exactly what I suggested.

Why standby when one can have a reservation? How is your plan to not have a seat on the earlier flight an improvement?

I had similar situations before on RTWs. So for example ticketed AAA-BBB, but then changed flight times and there was no AAA-BBB. Only AAA-CCC and CCC-BBB as a connection which i booked.
In all cases they just took my AAA-CCC coupon, issued two boarding passes and issued a handwritten extra coupon.
Never exeeded the max. miles (to my knowledge), but i dont remember anybody checking. Ticket was allways issued as First Class open.

Perhaps coz I have 'ethics.'

Two points:

1. Actually, isn't this theft of inventory? You are tying up a second seat that the carrier might have been able to sell.

2. Not all CSR's are dumbos. Had you presented to my counter, I would have most probably caught on to 'your scheme'... and as a result, pressed LOTS OF BUTTONS on the cash register.

What flight are you on again...???

I'm going to take it from the smilie that your post is one big joke. One of the nice things about flying full Y or higher is that the airlines actively encourage duplicate reservations to cover things like missed connections, early arrivals, etc.