Several aviation terms have their origins in the maritime industry, which preceded air transport.

Before the International Civil Aviation Organization (ICAO) came into existence in April 1947, the term "flag carrier" was used to identify airlines whose aircraft had the flag of the country in which the airline was based painted on their fuselages. This followed maritime laws that required ships to fly the flags of the countries where they were registered.

With the cross-border operation of aircraft, the ICAO established standards for the nationality and registration markings for all aircraft. All ICAO member states were assigned nationality markings.

TT was assigned 9Y; the US, N; Canada, C; and the UK, G. The registration markings immediately follow the nationality markings, are assigned by the individual countries and consist of alpha-numeric characters. For example, an L1011-500 aircraft operated by BWIA and registered in the US had the nationality and registration markings: N3140D.

All nationality and registration markings must be painted on one of the lower wings and on both sides of the fuselage, preferably on the tail of the aircraft, using clear and visible Roman capital lettering and Arabic numbers without ornamentation to specified sizes.

This allows the aircraft to be easily identified as either a friend or foe in the event the aircraft makes an unauthorised incursion into another country’s sovereign airspace and is intercepted by military aircraft.

All aircraft must have two identification plates made from fireproof material and attached to the aircraft, normally in the forward passenger door jamb. The first must be inscribed with the aircraft serial number, make, model and the name of the manufacturer. The second plate must be inscribed with the nationality and registration markings and the name and address of the owner.

In the event of a total loss of an aircraft in a crash, the plates can be used to identify the aircraft.

On September 1, 1983, a Boeing 747, Reg No HL-7442, on a scheduled Korean Airlines flight from New York City to Seoul via Anchorage, Alaska, was shot down by a Soviet Sukhoi Su-15 interceptor.

The aircraft was en route from Anchorage to Seoul, but owing to a navigational mistake by the crew, it drifted from its original planned route and flew through Soviet-prohibited airspace above sensitive military installations.

The Soviet Air Force treated the unidentified aircraft flying in the black of night as an intruding spy plane and destroyed it with air-to-air missiles, after firing warning shots. The Korean airliner crashed into the Sea of Japan, killing all 269 passengers and crew aboard.

As a result, the US altered tracking procedures for aircraft departing from Alaska. President Ronald Reagan also issued a directive making the American satellite-based global positioning system (GPS) freely available for civilian use.

Also, most aircraft now have logo lights installed, which illuminate the airline’s logo or name during night time to enhance recognition of the