How does a hot air balloon work?

The basic principle of ballooning is simple: Warm air rises. If warm air is contained in a lightweight bag it will rise until the temperature of the air inside the bag matches the air outside. As the air cools, the bag starts to descend. These days touring balloons carry propane tanks (burners) in the basket or gondola to control heating the air. They are equipped with an instrument panel with a compass, altimeter, fuel gauge, and more. This makes modern balloon rides safe and comfortable, although the burner does get warm and rather loud at times.