What is the primary concern when carrying cargo in an aircraft?

The primary concern when carrying cargo in an aircraft is that it must not obstruct control or damage electrical systems. This is crucial because any obstruction can interfere with the pilot's ability to operate the aircraft safely. If cargo shifts during flight and obstructs control surfaces or instruments, it can lead to a loss of control. Additionally, cargo that comes into contact with electrical systems can create hazards, including electrical shorts, fires, or failures in critical avionics. Ensuring proper stowage and securing of cargo is essential to maintaining safe operations in an aircraft.

The other options, while they might have their importance in specific contexts, do not address the paramount safety concerns that come with securing cargo during flight. Identifiability, dimensional limits, or the packing of cargo is secondary to ensuring unobstructed control of the aircraft and protecting sensitive systems.