Which situation corresponds with level 4 interference?

Level 4 interference is defined as a serious threat to the safety and security of an aircraft. This level is associated with actions that significantly endanger the crew and passengers, particularly those that compromise the integrity of the flight deck. Attempted intrusion into the flight deck represents a direct challenge to aircraft control and poses an imminent danger to all on board, thus qualifying it as level 4 interference.

The other scenarios listed—smoking on board, damaging airport property, and intimidation along with physical violence—do not reach the severity of directly attempting to breach the flight deck. While these actions are serious and warrant response, they do not pose the same immediate and critical threat to the safety of the flight that a flight deck intrusion does. Hence, the correct answer highlights the most severe level of interference with aviation safety.