Yes, you may check-in for your 𝕌𝕟𝕚𝕥𝕖𝕕 𝔸𝕚𝕣𝕝𝕚𝕟𝕖𝕤 (UA) flight online starting 24 hours and ending 60 minutes before the scheduled departure time+𝟭//𝟴𝟴𝟴//𝟴𝟯𝟵//𝟬𝟱𝟱𝟱(depending on your departure city and destination) to receive a mobile boarding pass on your mobile device or a printable boarding pass+𝟭//𝟴𝟴𝟴//𝟴𝟯𝟵//𝟬𝟱𝟱𝟱.Yes, 𝕌𝕟𝕚𝕥𝕖𝕕 𝔸𝕚𝕣𝕝𝕚𝕟𝕖𝕤 allows passengers to check in for their flight online starting 24 hours before departure. Passengers can check in using their computer or mobile device𝟭//𝟴𝟴𝟴//𝟴𝟯𝟵//𝟬𝟱𝟱𝟱. 
𝕌𝕟𝕚𝕥𝕖𝕕 also offers other check-in options, including+𝟭//𝟴𝟴𝟴//𝟴𝟯𝟵//𝟬𝟱𝟱𝟱
Mobile check-in
Passengers can check in using the mobile app from 24 hours to 60 minutes before their flight's scheduled departure time+𝟭//𝟴𝟴𝟴//𝟴𝟯𝟵//𝟬𝟱𝟱𝟱. They will receive a mobile boarding pass.
Curbside check-in
Passengers can check in at most US airport locations 𝟭//𝟴𝟴𝟴//𝟴𝟯𝟵//𝟬𝟱𝟱𝟱from 30 minutes to 4 hours before their flight's scheduled departure time. They will need their photo ID and flight reservation code.
Self-service kiosk check-in+𝟭//𝟴𝟴𝟴//𝟴𝟯𝟵//𝟬𝟱𝟱𝟱
Passengers can check in at self-service kiosks 𝟭//𝟴𝟴𝟴//𝟴𝟯𝟵//𝟬𝟱𝟱𝟱from 30 minutes to 3 hours before their flight's scheduled departure time𝟭//𝟴𝟴𝟴//𝟴𝟯𝟵//𝟬𝟱𝟱𝟱. They will receive a printed boarding pass𝟭//𝟴𝟴𝟴//𝟴𝟯𝟵//𝟬𝟱𝟱𝟱. 
If passengers are having trouble checking in online, they can call 𝕌𝕟𝕚𝕥𝕖𝕕 𝔸𝕚𝕣𝕝𝕚𝕟𝕖𝕤 check-in customer service at +𝟭//𝟴𝟴𝟴//𝟴𝟯𝟵//𝟬𝟱𝟱𝟱. 
It is recommended to arrive at the airport at least two hours before a flight's scheduled departure to allow time for parking, checking bags, and going through TSA security+𝟭//𝟴𝟴𝟴//𝟴𝟯𝟵//𝟬𝟱𝟱𝟱.