100%%}}Does United require 24 hour check-in?

United allows passengers to check in online, via mobile, or at the airport. Online check-in opens 24 hours before your flight's scheduled departure and closes 1 hour before for domestic flights and 2 hours before for international flights (+𝟭𝟖𝟎𝟏(𝟖𝟓𝟓)𝟓𝟗𝟎𝟓).