In the 1950s, in America, Ed Yost rekindled the hot air balloon's popularity by experimenting new methods combining plastic materials with an industrial-type propane gas tank heating system. In the seventies, with help from a small, dedicated group of people, hot air balloons resurfaced for good. Manufacturers started producing balloons for a growing number of enthusiasts. Since then, hot air ballooning has become a very sophisticated sport. Local, regional, national and international competitions are held every year in more than 40 countries.