Centenary of Universal Postal Union. (Soviet Union, USSR 1974)

Souvenir Sheet Centenary of Universal Postal Union. it reflects the thematic directions:

The Universal Postal Union (UPU, French: Union postale universelle) is a specialized agency of the United Nations (UN) that coordinates postal policies among member nations and facilitates a uniform worldwide postal system. It comprises 192 member states and is headquartered in Bern, Switzerland

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.