I am hoping to reserve my seat for a flight from YYZ to MUC later this week. The ticket is with Lufthansa but the code-shared flight is actually Air Canada.

I tried to reserve my seat with AC but it wouldn't recognize my booking number. Lufthansa did recognize my booking. However, reserving a seat with them is not possible since it's an AC flight.

Am I out of luck and have to take my chance at the airport?

Any advice is appreciated.

You have to ask Lufthansa what your reservation number for Air Canada is. I believe you can use that on the AC website to pick seats .

That is correct , you have a separate reservation number for each code share partner, you need the air canada portion to pick seats

There's very few cases when AC will allow you to select seats online if not booked on Air Canada's web site. That includes, at least until fairly recently, not sure if it's till the case, Aeroplan award tickets. So unfortunately, this will likely require a call to AC. This was supposed to be fixed a couple of years ago, but as I understand it, still isn't.

Note that AC also has terrible hold times even on a good day on the non-elite line. I would expect to budget 45 minutes at least for that. Trying off hours (I.e. Middle of he night) YYZ time is probably your best shot at a shorter wait.

We weren't able to reserve our seats as a UA codeshare in July. We tried the long phone call but no help there either. Its worth a shot but I wouldn't bet on it

I agree with asking Luft for the AC flight confirmation code. We have done the reverse as well. Booked my husband on AC but flight was an AC/Luft co-share. AC gave me the Luft confirm number and I was able to book seats for him. And I seriously begged that he not be given a middle seat.

Note however, that this was only for the Toronto to Frankfurt or Munich etc. part of the trip.

Since we were travelling onwards in Europe - but on Luft inter-European flights with AC codeshare flight numbers I was not able to his book seats.

He was SA Gold - but that only helped when it came to luggage, lounge access etc. - seats on the inter-Europe flights booked in Tanglo/Flex (or their version of it) could not be booked in advance. Nothing like receiving a confirm of your flights along with a notice about bumping to make you feel secure. Since I was travelling on a Business reward ticket, well I had seats the whole way!

Actually, you don't even need the AC record locator (confirmation #) - just the AC flight number, which you can look up on the AC website. Just give AC the AC flight number and your last name and they will be able to find the reservation.