What type of debris does FOD refer to that can be hazardous during aircraft operations?

FOD, or Foreign Object Debris, specifically refers to any foreign objects present on the runway or in other critical areas of an airport environment that can pose a hazard during aircraft operations. This can include items such as stones, pieces of equipment, tools, or even litter that can be ingested by engines or damage the aircraft's surfaces upon landing or takeoff. Identifying FOD as a risk is crucial for maintaining safety standards in aviation operations, as such debris can lead to significant incidents or damages.

The other options, while they might involve safety elements around aircraft operation, do not encapsulate the overarching definition of FOD. Fuel and oils, for example, are part of operational control rather than debris. Mechanical parts from aircraft are typically within a maintenance context, and passenger luggage is accounted for in terms of handling and passenger safety, not classified as debris that can cause hazardous situations on the runway.