The vacancy bid that closed in December of 21 had unfilled Captain slots in EWR,DCA,LAX, and SFO. At United you must be off probation and 500 hours to bid for Captain, so virtually anyone hired before Nov ish of 2020 would be off of probation, but some prob didn't have the 500 hours, as flying was still depressed in early 21. So, if you were hired in late 20 and actually flew, you could have held Captain on that bid. A few folks did bid it, but most at that level of seniority either weren't eligible or didn't want it.