A total of 91 helicopters, taking part in relief and rescue operations in Pakistan's earthquake devastated areas, have so far flown for 2,750 hours, officials said. Of these helicopters, 22 are of foreign countries, 18 of Non Government Organizations and the rest are of Army Aviation, Pakistan Air Force and Pakistan Navy. The helicopters taking part in the operation are MI-17, PUMA, Bell-412, Y-12, Sea King and Alouette. Twelve US helicopters, engaged in the operations, include five Chinook, three Black Hawk, Sea Hawk, two MI-17 and two MH 53. Two MI-17 of Kingdom of Saudi Arabia and two Chinook helicopters of Germany are also participating in the relief and rescue operations. Four MI-17 of Afghanistan after participating in the rescue operations have returned back. British Chinook helicopters recently joined the relief efforts. Officials said the 12 helicopters which were flown for 42 hours on first day when earthquake hit most parts of Azad Kashmir and North West Frontier Province (WNFP) evacuated 595 casualties. After that the number of helicopters has been gradually increasing and so is their flying hours. The Army Aviation and other pilots flying these helicopters have been flying at an average of 225 hours per day.