I know it seems like a weird question, and that the operating carrier should take care of its own passengers. However, I had an interesting experience recently which was not consistent with previous experiences, albeit with other carriers/ alliances.

Who do I approach for rebooking when a UA-numbered but partner-operated flight is canceled?

I had a UA-issued business class ticket from the US to EU. Both the outbound and return were operated by LH.

On the return leg, while at the gate, LH incrementally delayed the departure by 30 minutes several times then eventually canceled. (plane went tech).

An hour into the delay, gate staff insisted that the flight would still depart and that mechanics are working on the issue. They declined that I be rebooked on any of the other UA or LH flights to the USA. I had a meeting that night back in the US and wanted to still make it in time for dinner. The third time I asked (nicely), the gate manager sounded terse with all the requests from other passengers and he sent me to chill out at the lounge (which was packed with other business passengers from my flight).

Eventually, the flight was canceled so I approached the service desk at the LH lounge. Agent was nice but went on a long monologue on why she cannot rebook me. I killed her with kindness and pleaded my case, and she eventually called the LH service desk to "secure" me an alternate itinerary. She said that I should have physically gone down to that area myself but she was calling on my behalf out of courtesy. (Although when I went down from the lounge, physical service desk was closed!!!)

After printing out an alternate itinerary on UA. She told me that my boarding pass can only be issued by a UA staff since I have a UA ticket???

The new flight, instead of a nonstop LH flight from FRA to the US ended up being a one-stop, but all on UA.

[I thought that was weird. In the past, I was on a CX ticket with a canceled initial leg on AA, and AA rebooked me on a new itinerary with AA + JL; ditto when my DL-issued DL+KE flight from Asia got re-timed, KE rebooked me on one of their flights. Both carriers issued my BPs. Why can't LH on this instance? Something special with the rules of the UA ticket that I have???].

After printing the new itinerary, the LH lounge agent told me to go to gate Z16 where an active flight was departing and UA agent is most likely to be found. Agent said they were closed already. She sent me to Z25.

At Z25, I queued together with all the other LH orphans from my flight only to be told to leave them alone during their active boarding, after 30 minutes on the queue. She sent me to Z17.

Finally found the help desk beside Z17. Lady agent said she has no power to help that the canceled flight is my own problem. Her manager happened to be standing behind her who saw my paper itinerary and firmly told her that they were obligated to help me since it was a UA ticket. Original UA agent finally logged on to her computer. Took her 30 minutes to do so because she could not remember her password and did not know how to do a BP issuance, and the manager had to walk her through the whole process. All this time, there was a lady and a man behind me screaming about needing some help. Finally, manager told me that LH did an 'error' when they 'secured' the flight for me and put me on economy for my onward connection despite having booked business. I okayed that since I did not want to be stranded in FRA, and I just wanted to get out of there.

I got my BP then sat on a seat by an empty gate. I opened the UA app. I chatted with an agent on the UA app and told them what happened and he/ she restored my onward flights in business/ domestic first. Arrived at my destination 12 hours later, and missed my meeting!

Anyway, in these situations of IRROPS where I am holding a UA ticket but operated by a partner, who should issue my new itinerary and boarding pass?

Initially, I thought that the LH agent could not help me any further than 'rebooking' because I was on a ticket issued by UA and not LH. However, those on my original flight who were holding LH-issued tickets were given the same instructions by the lounge staff when they were rebooked.

Agent told me that 92 passengers on my flight ended up being stranded in FRA with no alternatives (same flight number the next day was already full).

I booked the original LH flight because I wanted to be in the nose of the 744 which I was able to do on the outbound. Glad that I got to experience Polaris on the return.

With US domestic flying, after a certain amount of delay, gate agents will often allow rebooking on an alternate flight, and sometimes even making announcements proactively.

I have several flights coming up which are booked through UA but operated by ANA. I am hoping no IRROPS, but if it happens, what should I do? I also know that this will not be my last Lufthansa flight.