volume of airspace that encompasses the entire operation, with sufficient buffer for any operational movement around the flight path, due to navigational errors, expected weather conditions and any other reason for deviating from the flight path
NOTE 1 flight volume refers to normal operations and is surrounded by the “contingency volume” (3.1.25) which provides a buffer within which contingency procedures are activated.
NOTE 2 flight volume is similar in concept to the EASA term ”light geography” which means the spatially and temporally defined volume of airspace in which the UAS operator plans to conduct the operation under normal procedures.
[SOURCE: UK CAA CAP 722D, Unmanned Aircraft System Operations in UK Airspace: Abbreviations and Master Glossary, 2nd edition, December 2022] 
BSI Flex 1903 v1:2023-08 formally released