European Airmail Conference - Blue (Belgium 1938)

Stamp European Airmail Conference - Blue it reflects the thematic directions:

A head of state (or chief of state) is the public persona that officially represents the national unity and legitimacy of a sovereign state. In some countries, the head of state is a ceremonial figurehead with limited or no executive power, while in others, the head of state is also the head of government. In countries with parliamentary governments, the head of state is typically a ceremonial figurehead that does not actually guide day-to-day government activities and may not be empowered to exercise any kind of secular political authority (e.g., Queen Elizabeth II as Head of the Commonwealth). In countries where the head of state is also the head of government, the president serves as both a public figurehead and the actual highest ranking political leader who oversees the executive branch (e.g., the President of the United States).

Cartography (/kɑːrˈtɒɡrəfi/; from Ancient Greek: χάρτης chartēs, 'papyrus, sheet of paper, map'; and γράφειν graphein, 'write') is the study and practice of making and using maps. Combining science, aesthetics and technique, cartography builds on the premise that reality (or an imagined reality) can be modeled in ways that communicate spatial information effectively.

A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes. Many maps are static, fixed to paper or some other durable medium, while others are dynamic or interactive. Although most commonly used to depict geography, maps may represent any space, real or imagined, without regard to context or scale, such as in brain mapping, DNA mapping, or computer network topology mapping. The space being mapped may be two dimensional, such as the surface of the earth, three dimensional, such as the interior of the earth, or even more abstract spaces of any dimension, such as arise in modeling phenomena having many independent variables. Although the earliest maps known are of the heavens, geographic maps of territory have a very long tradition and exist from ancient times. The word "map" comes from the medieval Latin Mappa mundi, wherein mappa meant napkin or cloth and mundi the world. Thus, "map" became the shortened term referring to a two-dimensional representation of the surface of the world.

King is the title given to a male monarch in a variety of contexts. The female equivalent is queen regnant (while the title of queen on its own usually refers to the consort of a king). In the context of prehistory, antiquity and contemporary indigenous peoples, the title may refer to tribal kingship. Germanic kingship is cognate with Indo-European traditions of tribal rulership (c.f. Indic rājan, Gothic reiks, and Old Irish rí, etc.) In the context of classical antiquity, king may translate Latin rex or either Greek archon or basileus. In classical European feudalism, the title of king as the ruler of a kingdom is understood as the highest rank in the feudal order, potentially subject, at least nominally, only to an emperor (harking back to the client kings of the Roman Empire). In a modern context, the title may refer to the ruler of one of a number of modern monarchies (either absolute or constitutional). The title of king is used alongside other titles for monarchs, in the West prince, emperor, archduke, duke or grand duke, in the Middle East sultan or emir; etc. Kings, like other royalty, tend to wear purple because purple was an expensive color to wear in the past.

Aviation is the practical aspect or art of aeronautics, being the design, development, production, operation and use of aircraft, especially heavier than air aircraft. The word aviation was coined by French writer and former naval officer Gabriel La Landelle in 1863, from the verb avier (synonymous flying), itself derived from the Latin word avis ("bird") and the suffix -ation.

An aircraft is a machine that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. The human activity that surrounds aircraft is called aviation. Crewed aircraft are flown by an onboard pilot, but unmanned aerial vehicles may be remotely controlled or self-controlled by onboard computers. Aircraft may be classified by different criteria, such as lift type, aircraft propulsion, usage and others.