Originally Posted by BoeingBoy
This shows Bombardier's standard seating arrangements for the CRJ-900 (scroll to the bottom of the page). While I certainly don't know, I suspect that Mesa has the standard 86 seat interior - it's the upper of the two diagrams.
Jim
Bombardier CRJ-900
I can't find the seatmap for the Mesa 900's on seatguru, so BB's link should be ok.