Today I checked in online for American Airline flight to San Francisco and Cathay flight from San Francisco to Hong Kong. For AA, you need to fill out your Family and First Name as well as the AA Record Locator on the left of the AA itinerary Ms. Pham gave us. AA will send you the printable boarding card or mobile boarding card
https://www.aa.com/reservation/flightCheckInViewReservationsAccess.do
For Cathay Airline, you need to fill out your Family and First Name, your travel documents, and Airline Reference, most of us will be seated on Row 65, I picked 60C which is next to the aisle.
https://www.cathaypacific.com/cx/en_HK/manage-booking/check-in/check-in-now.html
Hope this would help, counting down 21 hours to leave Springfield MO for San Francisco CA