United and Air Canada seating on the same itinerary
For a sector identified as Air Canada-operated, start with Air Canada’s advance-selection conditions. For United seating options, United describes seat changes among the functions of its app. Air Canada Basic carries an advance Standard-selection fee. Its Standard-fare charges depend on the itinerary, while Latitude, comfort, and Flex include Standard selection. Those Air Canada conditions should not be used as a United fee table, and a United app feature does not establish an Air Canada fare benefit. If one carrier’s system cannot show the other sector’s map, ask which reservation reference and channel should be used for the operating flight. The cited sources do not establish that every cross-carrier booking is retrievable or that all seat purchases synchronize automatically. Confirm the traveler, flight, and existing assignment before authorizing another payment.

Important unknowns
- Current partnership scope, reservation-reference interoperability and synchronization were not verified.
- Live canonical owner and nearest-page content are UNKNOWN because the sitemap index could not be retrieved.
Sources and last checked
- Online advance seat selectionhttps://www.aircanada.com/ca/en/aco/home/fly/onboard/preferred-seats/online-advance-seat-selection.html
- United Airlines app: developer descriptionhttps://apps.apple.com/us/app/united-airlines/id449945214