I always like to look at real numbers... So, the most junior flow selected last time was April of '99 hire. That's 16 years to flow. However here are the numbers from the Envoy flow list. Estimating 33 month (flow (~30) + attrition leaving (~3)) we have.
1999: 158 pilots (4.8 months)
2000: 146 pilots (4.4 months)
2001: 78 pilots (2.4 months)
2002: 0
2003: 0
2004: 103 pilots (3.1 months)
2005: 55 pilots (1.7 months)
2006: 49 pilots (1.5 months)
So in 1.5 years (17.8 months) it will drop from 19 years (2015-1999=19) to 11 years (2017-2006) street to AA through Envoy.
Continuing from there and increasing the number who flow/leave to 40 (15 flow + 25leaving) you hit the following numbers
2007 249 pilots (6.2 months)
2008 159 pilots (4.0 months)
2009 0
2010 123 pilots (3.1 months)
2011 351 pilots (8.8 months)
2012 8 pilots (included in 2013 numbers)
2013 95 pilots (2.6 months)
2014 87 pilots (2.2 months)
So that leaves 2 years and 3 months (26.8 months to flow).
If you are hired off the street today at Envoy, and nothing else changes, you should be able to flow to AA in 3 years and 9 months.
Wow, I'm even surprised at that!