One more thing you should be aware of, pilots are given the cargo manifest by the load master before the flight. Sometimes, the cargo contains temperature sensitive loads and thus the crew can adjust the temperature of the cargo hold.
This holds true for cargo and passenger aircraft.
For example, if transporting live animals the temperature is increased above the "normal" range.
If your item is suitably marked and you have notified the shipper of the same, they will ensure that it is secure during the flight. However, as mentioned by @jpatokal - your main worry would be the time it spends on the ground, being driven to-from the cargo hold, etc rather than the flight on the aircraft.
Check with your shipper to see what they can do to prevent any damage to your item.