with one load of passengers. Tethering techniques depend on the balloon manufacturer's instructions and wind conditions. Tethers can be attached to the basket, burner support, or the top of the envelope. A "night glow" is a tethered flight in darkness to enhance visual effects. While typical day flights use the main valve, using an efficient blue flame, at night tethered pilots use the liquid valve "whisper burner" ("cow burner", as it does not startle livestock), creating a spectacular bright orange flame. Though tethered, a balloon is considered a registered flying aircraft when it leaves the ground. Events There are many regular gatherings of balloons and balloonists around the world. Most of these events are held on an annual basis. The festivities provide both a place for balloonists to interact as well as a venue for entertaining spectators. Events range in size from a few balloons and no spectators to hundreds of balloons with hundreds of thousands of spectators. The largest such event in the world is the Albuquerque International Balloon Fiesta, held every October in Albuquerque, New Mexico, followed by the Grand Est Mondial Air in France. The Bristol International Balloon Fiesta is another notable European event of this nature. Gallery Ballooning in the world See also Fédération Aéronautique Internationale List of balloon uses References Notes Bibliography The Science and Art of Hot Air Ballooning by Jackson and Diehtl, Garland Publishing Inc, 1977 How to Fly a Balloon by Stockwell and Kalakuka, Balloon Publishing Company, 1999 Balloon Ground School Home Study Manual by Stockwell, and Kalakuka, and Grady, Balloon Publishing Company, 1997 The Balloonist: The Story of T. S. C. Lowe – Inventor, Scientist, Magician, and Father of the U.S. Air Force, by Stephen Poleskie, Frederic C. Beil, Publisher, 2007. External links FAI International Balloon Committee Balloon Federation of America International Aeronauts League Possible prehistoric Nazca hot air balloon Balloon quotations Articles containing video clips