Economic prosperity brings greater demand for travel. As people get wealthier, they can afford to travel further and more often. In the case of aviation this trend has been amplified by technological advances, cost efficiencies and strengthened competition within the industry, which have brought air travel within the reach of many million people. In an era of increasing globalization, foreign travel - whether for pleasure or on business - is now a common experience. The increasing affordability of air travel has opened up new destinations and possibilities. Further, it has also expanded people's horizons, opportunities and expectations. As a result, air travel has shown a three-fold increase over the last 30 years. The availability of sufficient airport capacity is an important constraint on future growth. However, even at current levels of use, many airports in the U.S., Europe and few airports in Asia Pacific are becoming increasingly congested as they attempt to cope with rising passenger numbers. In some cases, the capacity of terminals and runways is at, or near, saturation point.