Price is the most important factor influencing demand for airline seats and cargo space since deregulation. Economists have emphasized the role of price in determining demand levels. Pricing in the airline industry is complex due to the industry's transition from regulation to deregulation. Demand is defined as the quantity consumers are willing and able to purchase at various prices over time. There is an inverse relationship between price and quantity demanded known as the law of demand. While price is key, other non-price factors like passenger preferences, the number of passengers in a market, passenger income levels, and competitors' prices also influence airline demand.