Additional Services (BOW Calculation)

Why not just use the Basic Empty Weight (BEW)?

Aircraft have items on board for every flight that are not included in the basic empty weight (BEW). For example, coffee, ice, drinks, navigation charts, and crew. These items must be included to insure that the resulting takeoff weight and c.g. is correct.

The example shows a typical basic operating weight (BOW) calculation for a Boeing 727. The additions for the BOW are 2,700 lbs!, a significant amount.