Allow filtering of inactive aircraft in dropdown lists.

When creating a dropdown list custom field one has the option of selecting between a list of bases, departments, aircraft, custom options or a reference from an existing field.

If the option for bases is selected there is a checkbox to include inactive bases.

If the option for aircraft is selected there is no checkbox and inactive aircraft are included by default.

There should be an option to choose whether inactive entries are included or not when the aircraft option is selected.