Adding a segment to one of the two passengers on a booking

Is it possible to add a segment for just one passenger at the beginning of the itinerary? Originally there are two passengers with exact same itinerary.

Of course it is... as long as the airfare is changeable, and the itineraries are split, and you are willing to pay the change fee and new fare.

Unless of course you are still in the first 24 hours of your paid reservation, or are upper elite and using an award ticket... then it doesn't cost as much.

Thanks Geo, I didn't state the question very clearly. It is an award itinerary with two passengers. Now I need to add a segment for one of the passengers. Would UA allow this on one itinerary? How much fee am I expecting?

You'd need to split the itinerary, and unless you're elite, there is a $75 fee. You'll also need to still follow routing rules (if there are any) for the route.

There are details here:
http://www.united.com/web/en-US/content/mileageplus/awards/travel/ticketing.aspx

It's a fundamental assumption of all the major res systems that multiple people traveling on one reservation will have the same itinerary. That's why you'd need to do one of two things:

1) Split the res to add the segment;
or
2) Create a new res for the new segment.

There are advantages and disadvantages to each approach.

Thanks everyone. I think it's cheaper to redeem Avois points for that segment separately (7.5k for coach, 15k for Biz).

Leave plenty of connection time (enough for a few alternate pathways) on that first segment add-on. if it is late, your main trip will be toast.

This is generally good advice, but the extent of the risk depends on the alliance (oneworld claims to protect people on different PNRs), the carrier (DL has told be that they would take care of me if I have two separate DL tickets, but I haven't tested this), and your status.

AFAIK to be on the same PNR, everyone must be booked on exactly the same flights on the same fare. So one cannot be a award ticket and the other not, or one in a higher fare class.

You can link PNR's on purchased tickets and that is certainly the way to go. I do this on my trips to Perth, breaking the ticket in SIN, and picking up a new ticket saving $6-8k on the trough fare. When I've tried to link on awards... nope, no luck.

You can do that but it doesn't really actually do anything useful for the itinerary.

If it is different airlines maybe, but my experience has been different for same metal multiple tickets.

Any airline can add the SSR notes to "link" the records. My experience has been that it doesn't really matter. When on same carrier metal then I've always been accommodated, link or not.

Do you have a situation where the linking actually helped something happen that you don't think would have otherwise worked?

Yes. I was on a circle pacific fare which requires a west coast departure and return. As I don't live on the west coast I had to purchase a separate ticket to get there from and back to IAH. In booking it with the elite desk (I wasn't GS at the time), I offered to leave extra space to accommodate flight delay/interruption on the return due to the separate ticket. I was told that that would not be necessary as even though they were separate itineraries, once they were linked (their words) I'd be covered. Now, what ended up happening was CP fare purchased in C and confirmed, and IAH-SFO-IAH purchased in Y then linked. As it turned out, the SYD-SFO flight was late. I missed my connection but it got rebooked, next flight out (plus, they gave me a $250 voucher for the inconvenience). Would it have happened without the link? I don't know, but I want to think that it made a difference to link.

I'd also wager that apart from itineraries with special fare restrictions and departure points, linking on the same metal is better done as a merge of the two. Cross-metal, e.g. UA to TG... not so easy.