Used A/C Numbers

Hi Does anybody know how the number of used A/C are determined?

The number that is shows as produced for the 737- 400 falls well short of Boeing's production figures even when you combine the numbers for the BGW & HGW.

The same happens with the DC10-30.

Any ideas?

These are the aircraft still in service at the date of the dataset compilation.

Thnks for the info. That makes sense.

Those are the aircraft that were inserted into the AirlineSim game world. The numbers bear no resemblance to real life numbers.