What is the relation between number of crew members (pilots and attendants) and fleet size in airlines? Taking into account relevant elements like the fleet size or the type of flights (short or long haul, passengers or cargo, ...), do airlines use typical ratios between the number of aircraft and the number of pilots and attendants?



Clarification for the type of elements I'm looking for:


Northwings has 120 passenger aircraft and 720 pilots, this is comparable to other US airlines with modern aircraft (6 per passenger aircraft).  
There are between 4 and 10 Captains per passenger aircraft. This is dependent on local labor laws and unions.  
4 to 6 F/O for cargo aircraft (and no attendants because no passengers).  
A380 are atypical at Thing Air with 700 flight attendants for 10 aircraft of that type.  
Count 25% less for low cost airlines in the Middle East due to less restrictive labor laws and extended working time.  


(Figures are for illustration, I've no idea of what the actual values are.)
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