To enter United’s premier Polaris Lounge after an upgrade, your upgrade must be officially cleared into the Polaris Business Class cabin on a long-haul international flight. In 2026, simply being on a "waitlist" or upgrading to a domestic First Class seat does not grant access. You must present a boarding pass showing "United Polaris" for a same-day international departure. The Polaris Lounge is a high-value "sanctuary" featuring à la carte dining and daybeds, distinct from the standard United Clubs (which you can enter with a one-time pass or membership). If your upgrade clears at the gate, you unfortunately miss the lounge window, so the "pro-move" is to use PlusPoints or MileagePlus miles to confirm your upgrade well before you arrive at the airport terminal.