Seat Selection using United Frequent Flyer Miles on other airlines?

Have you already secured your tickets? If so, pull up your reservation on the United site. Somewhere on the screen there will be an option to "see other airline booking codes". Make a note of those other codes and then head to the Aer Lingus and Swiss sites and use those codes to select your seats. You call also call the individual airlines but make sure you know the booking codes.

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This is all done online through their web sites except as noted. Emails tend to get lost in the cloud. Phone calls have fees.

You need to get the PRN for each flight from the airline flying that leg. That is the 6 character ID that you will see on your flight reservation confirmation. United will probably have one on the reservation you made through them using your miles and will probably have the ones for the individual flights as well.

Once you find those, you go to the web site of each individual airline operating that specific flight and you should be able to look up your reservation there. They may require you to create a frequent flyer account with them to do anything further, but you should be able to pick seats following their guidelines

If you don't find the PRN, you will find the actual ticket numbers in your United reservation. Then you call the airlines and request the PRN that goes with each ticket. Then do as above.

Or you just wait until check in time and hope you get lucky when you check in online and accept the seats they give you.

Note that some airlines do not allow picking seats in advance at all, while others require a payment to pick any seat.

Also restating: You cannot get your seat assignment on the United web site, through their phone customer service or any other way in advance for any code share flights. You MUST do so directly with the airline actually flying the route.

I have no personal experience with Swiss Int'l, but I agree that getting the record locator for the Partner airline is the key. In some cases, I was able to log onto the Partner's website and select my seats, a few days after getting the flights through the United Website. One time I had to telephone Lufthansa, they did not complain about my making a live phone call instead of using the internet (which would of course save them "money".) Note that the Partner code may not be instantly available.

The point is that once you have the code, you are likely to be able to view and modify your flight record with your name and the code, on the Partner's website.

I hope you don't have to test this, but I do recall, years ago, that non-revenue passengers tend to be "at the end of the line" when there is some sort of major disruption, like a flight cancellation or a volcano eruption. Just mentioning.

EDIT: When I used the term Partner, I meant the Star Alliance airlines that United can apply Freq. Flier miles to. I did not mean specifically United flights that happen to have Codeshare numbers on other airlines, or vice versa. I'm sure many of my Lufthansa second-segment flights have not had codeshare numbers, say, Frankfurt-Cologne.

Edit 2: See this nearby post:
https://community.ricksteves.com/travel-forum/transportation/sharing-lessons-learned-airline-travel-on-recent-italy-trip

To avoid confusion, it's PNR for Passenger Name Record. Think of a PNR as a virtual folder that contains all the ticket information for flights purchased at the same time for the same passengers for the same routing.

As pointed out above, the key to this is having the confirmation number/booking code for each partner airline (different airlines use different terms for this, but they all have one - confirmation number, booking code, reference number, PNR, whatever - if in doubt try any of these terms). The various airlines' systems do not speak the same language, so the code for your United reservation may be (usually is) completely useless for the partner airline's system.

You booked using United FF miles, so start with United. Log in to their website using your FF account. Click "My Trips". Your flights should be listed there - click the one you need info on. While you're there, note the United Confirmation Number - keep this and have it handy, you might need it in a pinch. There should be a link for "Other confirmation numbers" or some wording to this effect (I don't have it in front of me right now). That's where you will find the code for the partner airline; it's usually (not always) a 6 digit code. Record this partner airline confirmation code - it is the key to everything you need to do with that airline. If you can't find it on the United website, call United and ask them for it - they should be able to give it to you (try the website first though, you will avoid the long phone hold).

You will want to have this code handy whenever you deal with the airline you're flying on - and not to put too fine a point on it, but once your flights are booked, you are done dealing with United: when you deal with the airline you're actually flying, leave United out of the conversation, any mention of that will just confuse them and complicate things for you.

I can't help you with either Aer Lingus or Swiss, you will need to try them yourself. For most airline partners, just go to their website (remember, you're done with United), look for a link like "Manage my booking" (almost every airline has this on their website). You will usually need to enter your confirmation code (for that airline) and your surname. Once you do that, you should be able to access your booking. For most (though not all) airlines, you can then pick seats, check in online (usually within 48 hours - exact details vary) and perform other minor tasks. Picking seats is most important. Try to do this ASAP if you can. If you can't, call the airline (their US office, find the contact number buried on their website) and ask them about picking seats.

This should work for most airlines. A few airlines have weird rules that restrict how/when you can pick seats (eg: can only pick seats within 90 days before the flight, or within 48 hours of departure, etc.). If you have trouble, call and ask about this. Only a few require you to do this upon arrival at the airport (which really sucks). Most likely you can do this all on the website once you have the necessary confirmation code. Picking seats once you get to the airport is almost a guarantee you will get a really bad seat, so try hard to pick your seat ASAP, not at the airport when the only seats available may be a middle seat in a non-reclining row next to a stinky toilet.

Good luck.

Someone has already noted that some airlines do not allow pre-assignment of seats on code share flights. I know specifically that United code share flights with Austrian Air do not. Despite multiple calls to both airlines we did not get seat assignments until we checked in at the airport for the Austrian Air flight. The United customer service ?? person said that their computer systems were "not compatible".

We did OK and were seated together but they were not good seats and we had booked 7 months out just so we could get good seats on a transatlantic flight. Frustrating and annoying. Another couple we met in the airport were split up. Book direct with the airline when possible. Otherwise, ask questions up front.

On the other hand, a code share (FF points) booking on United for an Asiana flight to India worked fine. Dumb luck in this case.

I had the same issue Robbie did back in May on a Lufthansa flight that was part of a United booking (paid-for, not frequent flyer). I had to wait until 24 hours before the flight to choose a seat. I was still able to get an aisle seat; I'm not picky and was traveling alone, so it worked out OK.

On other codeshare flights I have had no problem choosing seats shortly after ticket purchase, so it depends on the operating airline.

I know specifically that United code share flights with Austrian Air
do not.

No longer. You can now select your seats 48 hours before the flight via the Austrian site.

"Code share" is not the same as "partner" airlines booked with frequent flyer points.

Bottom line: it depends on what airline you are flying on; it may also depend on what airline you booked your flight through. These are separate issues. You need to explore your options (which do change over time) with the specific airline you're on. Lots of variables so it's impossible to make firm predictions.

It is common that for flights within Europe, you cannot select seats before check in - even if you booked direct with the airline operating the flight. So, while you should certainly try, don't panic if you can't get seats now for the Dublin to Lisbon or the Lisbon to Zurich legs.

One other thing you want to check into before you fly is what happens if you have a delay or cancellation on any of your legs. I flew on miles (6 people) to Italy in June and United delayed our return flight from Rome 12 hours. I was able to get on the phone with United’s 1k line and get us all rebooked with economy plus seats for another flight close to our original departure time. I don’t know if I would have been able to do that easily on a code share. In February, I flew to Australia and onto Singapore on a business class ticket, code share with Singapore. When there was a flight delay and I wanted to get on a different flight, even though there was a seat on Singapore, because it was a code share, I could not get the seat. Now when I have a code share, I ask what happens when there is a delay, who do I call before I get delayed at an airport.

If you booked on United then you need to call, AerLingus, swiss air etc forthose flights.
2 days ago I called aer lingus for my flgts booked on United air online however lie u no sets. I called aer lingus to secure my seats. They charged me45.00 for ea international leg, and 12 within Europe.
Mine was a revenue tix, hopefully they will not chg u. But it is very advisable to get your set selection secured. Originally they had me in the last row in the middle, prob the worst seat on the plane.
Gd luck.