Originally Posted by
WineCountryUA
This is a gray area.
Your dad has access as *G on international itin and with UC membership access. Guest for a *G must on the same *A departing flight as the *G. However, the UC access does not explicitly state that same requirement. Some have reported success when not on the same flight but it is easy to see the lounge agent applying *G requirement. Best one can say its it is a worth a try.
Just to circle back on this, we were successful at the C10 lounge at ORD.
My Dad used the automated gates, scanned his boarding pass and said +1 guest, I scanned my NH F boarding pass from the flight we just arrived on (figured it was worth trying that vs my unconnected AA flight) and the automated gate accepted that as valid and let me through