CAO
Dangerous goodsCargo Aircraft Only
A label meaning the goods can only fly on freighter aircraft, not on passenger flights.
In practice
Some dangerous goods are forbidden on passenger aircraft but allowed on freighters in larger quantities. CAO shipments need the orange CAO label and can only be booked on freighter services, which limits routing and raises cost.
Seen in the wild
UN3480 lithium ion batteries Section IA are CAO. No passenger flights available.