UA is eliminating fixed-mileage upgrade awards. Nobody knows what the new system will look like. To answer your specific question, 30K miles per person, each way, was the highest amount charged under the old system, and it applies to any Economy fare class except Basic Economy. Basic Economy fares can’t be upgraded. (UA announced that the old system would change in November ‘25, but so far the new system seems identical. We’re all waiting for the other shoe to drop). I do not recommend buying a more expensive economy fare to try to preserve miles for the upgrade — you had to get into very expensive fares before the miles dropped.

Well… neither? Both?

In advance of travel, UA can choose to open upgrade space (into either PE or Business class, or both). That upgrade space is first-come, first-served; anyone who sees it can get it by requesting the upgrade. However, they’re loathe to do so, especially at peak times. Therefore, most upgrade requests go onto a prioritized list. UA can clear from that list at any time, but it’s most common in the ~36 hours prior to departure. You can clear an upgrade all the way until departure — if there are no-shows, UA gate agents will come onto the plane to upgrade passengers even after boarding.

Note that the prioritization of the list is going to affect you: it’s prioritized by MileagePlus status level and then by fare class. Anyone with MileagePlus status will be ahead of you for an upgrade, as will anyone who paid for a more expensive economy ticket. “But wait!” you ask. “You said not to buy a more expensive ticket!” I stand by that recommendation, especially if you don’t have status. The vast majority of UA upgrade requests are made by passengers who do have status — most of them Global Services or 1K, because they both get dedicated upgrade instruments called PlusPoints, giving them a lot more upgrade opportunities. And UA regularly sells out — or even oversells — the PE cabin. The only way your fare class would help you is if there were sufficient seats to clear everyone with higher status, and there was still one seat available, and there was someone else at your status level with a higher fare. That’s a lot of conditions; it’s far more likely that nobody clears except for maybe a GS or 1K member or two, or that everybody clears.