Aircraft Graffiti

Aircraft graffiti is graffiti on the outside of an aircraft or in the cargo bins, usually written by airport ground staff. Typically, the graffiti take jabs at ground staff at other airports, at other employees or supervisors, at airline managements, etc., and is usually intended to be humorous rather than offensive. During labor disputes, pro-union and anti-management graffiti are also common.
Although rarely seen by the travelling public, aircraft graffiti are very common and almost every commercial airliner is tagged in some way, most often in the cargo hold. Other common areas for the graffiti (these are usually written in the dirt or grease on an aircraft) include the engine nacelles, the fuselage under the wing, fuel panels, and landing gear panels, as well as any area of an aircraft where the ground crew work. One well-known case of aircraft vandalism occurred during the merger of US Airways and Pacific Southwest Airlines, when PSA employees painted their company's trademark "smile" onto US Airways aircraft formerly owned by PSA.
In military aviation, fighter crews are also known to write "messages" on the bombs and missiles shortly before leaving on a mission. For example, fighter crews during the U.S. invasion of Afghanistan wrote things like "Eat this, Osama" and "High jack this fags" onto bombs which were dropped during the campaign.