In 1980, postal inspectors investigated the mysterious disappearances of registered mail from commercial aircraft. The case was cracked on May 14 at the Atlanta airport when a huge trunk marked “musical instruments” accidentally opened as it was unloaded, revealing stowaway William DeLucia.
The U.S. Postal Inspection Service
Mid-Flight Theft

When this trunk popped open, the stowaway was discovered with his oxygen tank, food and a flashlight. Law enforcement officers, including postal inspectors, were called in to investigate.

The airliner cargo hold was pressurized, but the cautious jack-in-the-box thief carried this oxygen tank with him just in case.
The “jack-in-the-box thief” would emerge from his trunk mid-flight to steal mail. On this trip, he had loaded over $350,000 worth of items into empty luggage checked in by accomplices. Authorities arrested DeLucia and the two men who showed up to claim the luggage and trunk.