A 45-minute hot-air balloon flight over the River Nile and across the Valley of the Kings has long been considered the highlight of a tour to Luxor - one of the top tourist destinations in Egypt. Most flights are scheduled around the sunrise or sunset hours and are extremely popular with foreign tourists, a manager from SindBad Hot Air Balloons in Luxor said. Competition has intensified in recent years as eight operators battle each other for business. The number of tourists to Egypt plunged following unrest in early 2011, driving down Egypt's tourism revenues by as much as 30 per cent, according to government figures. Many companies cut balloon fares to win customers. The intense competition had raised concerns well before yesterday's tragic accident. A UK balloonist who has flown in Luxor wrote a guide to hot-air ballooning for the popular Tripadvisor website in 2011, warning of safety issues. "Some companies are now trying to do flights for only 30 minutes or so - so that they can land quickly and get their next balloon up as soon as possible. In this way they might squash in four or even five flights in the two-hour flying slot before the temperatures get too warm after sunrise. In my view, as a pilot, this is not a very safe practice as the latest flight of the morning runs the risk of encountering thermal winds which makes for bumpy landings or worse..." she wrote. The manager from SindBad Hot Air Balloons said local authorities grounded all flights immediately after the crash. He said on normal days, the company needed to seek air traffic control's permission before they could take off, with weather conditions a factor. Luxor has reported several balloon accidents in the past, the most serious in 2009 when 16 tourists were injured in a crash landing. In 2010, a balloon crashed into the River Nile, with no serious injuries. The nine Hong Kong victims killed in yesterday's tragedy were five days into their 10-day tour.