Please correct me if I 'm wrong but I believe UA likes to price all partner (but not JV) tickets based 100% mileage accrual, so these tend to be higher fare classes than if you were buying straight from said partner.

I see that JV partners like ANA actually pricing is very similar if not identical to UA, but other carriers like OZ will be a lot more expensive on UA website. I'm guessing SQ doesn't have JV with UA?

In most case, by the use of plating restrictions, the partner is limiting UA's access to discount fare classes.
SQ is a classical example of this limitation -- created by SQ, not UA.

Booking United Flights with Star Alliance Partner
 

I’ve been tracking the price of a UA flight on Google flights that happens to also be a codeshare available on Air Canada. The price of the AC-stock flight is 25% less than the 016-stock flight on United.

1. If I book this UA flight via Air Canada, will I get to use my 1K benefits?
2. Curious, who sets the price on the codeshare tickets? Never have seen such a big price discrepancy before.

I’m sure this has been answered before, apologies in advanced.

Yes, except you will need to deal with AC for ticket issues and you will not get UA's change policies.

Codeshares have access to different inventory and if the lower fare class has sold out on UA, you can see this. It will likely readjust soon.

Thanks! I couldn’t tell what fare class the AC ticket was during the booking process. Don’t know if there is an “expert flyer mode” equivalent over there.

Interesting on the codeshare inventory access.. didn’t know that. Now I’ll be sure to check UA codeshares on partners before booking.

It is normal to see UA codeshares more expensive than AC native flight numbers. UA does not open up K, G very often. I have seen differences >25% on transborder flights. Earning miles will be MUCH better in most cases on a 016 UA ticket. I sometimes book outbound UA codeshare and inbound AC code to get the 016 ticket and 1/2 the price-difference

Looking at 2 RT tickets in premium economy EWR-LHR in August. I can currently buy United flights on the Lufthansa website $360 cheaper (per person) than buying direct on the United site. Any downside to booking via Lufthansa? These are the cheapest tickets I've seen thus far beating any other airline on the route.

I have no status on either airline. I haven't bought premium economy on any airline before and usually don't purchase this far out for economy, but the PE cabins are small and I'm presuming (maybe wrongly) that prices won't drop much and I should grab the tickets now.

It is generally easier to handle schedule changes if the you are booking with the flight operator and not a codeshare.

Another advantage booking with UA, is it has better policies on voluntary cancellation and rebooking. Not sure what the LH fees are nowadays but UA has none. And any flight credit will have to be reused with the ticketing carrier .

If you have no schedule changes by the carrier or yourself and fly without any issues, then there is no difference. However if you or carrier starts making changes or irrops happen, the can be a difference. Whether the risk of those situations are worth the higher fare is a decision for you