Hello, thank you for your help.
I will be flying from XIY-PVG-SIN.
XIY-PVG is operated by Air China, booked through United Airlines
PVG-SIN is operated by Singapore Airlines, booked through Singapore Airlines.
Will I be able to interline my luggage upon check in at XIY through to my final destination? Air China is a codeshare partner of Singapore Airlines, but the flights are ticketed separately.