Odd occurrence just now. I'm flying IAD<->YYZ tomorrow for a day trip (no overnight). I'm in the 24 hour window for the outbound leg, so I checked-in via the app on iOS. It let me check-in for both legs even though the inbound flight is in 34 hours. It shows me as #1 (and the only member) on the upgrade list for the inbound flight. Adding to the oddness is the app refuses to give me the option to see my boarding pass for either segment (so I can store it on my phone). The only option on the boarding pass printing screen is to email it. I choose the option and no email is sent.