What is the relation between number of crew members (pilots and attendants) and fleet size in airlines?
My answer may not directly answer your question but from MIT's The Airline Data Project, I extract data for year 2014 and put in table as follow:

Employees Per Aircraft                                  Southwest    United    American Airlines   Delta Airlines    Jetblue Airways
----------------------------------------------------------------------------------------------------------------------------------------
Pilots &amp; Co-Pilots (Crews)                              6.0          8.3       6.8                 7.4               6.5
Flight Attendants (Crews)                               5.9          8.8       7.3                 6.8               5.0
Maintenance (Inhouse)                                   3.5          10.5      17.4                11.4              3.8
Passenger, Cargo and Aircraft Handling (Inhouse)        29.2         63.9      30.7                36.7              27.1
Other (Inhouse)                                         6.9          6.9       10.8                18.1              10.0
----------------------------------------------------------------------------------------------------------------------------------------
Total                                                   70.9         132.2     98.1                107.5             68.2


note that total number of crew does not add up with each type of crew in the table

Hope it gives you some idea about the ratio of pilot and flight attendant