A friend (1K) is mid-flight on an INTL route to the US, with a connection at ORD. The flight is ~1h early, and so catching an earlier connection onward domestically seems possible, but tight. Can any steps be taken officially via the app to join standby? Can I call the United line on their behalf to get officially added? Or should they just wait to sprint to the gate and talk to the agent? Thank you!