Ok I found this on the internet. So average is about 13,5 pilots/plane.
Airline**************Pilots/plane
BA****************** 14,5
Ryan air********** 11
United*************15.5
Delta***************14.5
American******** 13.25
Easy jet***********11.2
Continental**** 12.5
USAirways***** 11.75
Southwest****** 10.5
Air tran***********12.5
Singapore airlines 21
Airline comparison charts