An airline can only sell seats on an airplane prior to departure. Once the plane has left for its scheduled flight, any unsold seats on the plane lose their inherent value as an empty seat never can be utilized (and charged) after departure. The fact that service capacity cannot be stored for later consumption or sold at a later point in time illustrates the characteristic of services.

The business cycle is the periodic but irregular up-and-down movement in economic activity, measured by fluctuations in real gross domestic product (gdp) and other macroeconomic variables. a business cycle is typically characterized by four phases—recession, recovery, growth, and decline—that repeat themselves over time. economists note, however, that complete business cycles vary in length. the duration of business cycles can be anywhere from about two to twelve years, with most cycles averaging six years in length. some business analysts use the business cycle model and terminology to study and explain fluctuations in business inventory and other individual elements of corporate operations. but the term "business cycle" is still primarily associated with larger (industry-wide, regional, national, or even international) business trends.

Asolar eclipse occurs when the moon gets between earth and the sun, and the moon casts a shadow over earth. a solar eclipse can only take place at the phase of new moon, when the moon passes directly between the sun and earth and its shadows fall upon earth's surface.