not sure if it still is happening, but two pilots in my NH class last year leveraged a CJO with UA and DL to get a class date almost 2 years ahead of their AA flow. FWIW they had PIC time from a prior job and Envoy wasn't their first airline but still has low time. Also I know that his happens at Endeavor for the flow to DL also. (Had two Endeavor Captains in my class that couldn't get to Delta sooner so bailed to AA.).