For those who follow such stuff, FAA's Air Traffic Control System Command Center (ATCSCC) posts advisories for North American Airspace - including advisories on volcanic activity.

Consistently for quite a while, Popocatepetl in Mexico has been posted multiple times daily with such an advisory.

I'd note that the 03/14/23 US/MEXICO OUTLOOK_FYI indicates that additional volcanic activity was observed.up to FL220.

So, question is, will UA continue this waiver, add a new one or let it age out after tomorrow?

David