Why baggage decides the aircraft more often than seats do
Charter aircraft have two capacity limits: seats and hold. Groups reliably think about the first and underestimate the second. A squad of thirty with playing kit, medical equipment and analysis gear, or a touring band with backline and cases, can exhaust the hold of an aircraft with plenty of spare seats.
There are two separate constraints inside the hold as well: volume and weight, and either can bind first. Instrument and production cases are bulky but relatively light, so they hit volume limits. Sporting equipment, tooling and battery packs are dense, so they hit weight and sometimes floor-loading limits. The aircraft that suits each is not necessarily the same.
This is why we ask for kilograms and item counts rather than a general description. 'Normal luggage plus some equipment' cannot be sized against a hold; a list can.
