MANILA (Reuters) - Philippine commandos and law enforcers have practiced hostage negotiations and the storming of a commercial jet to free American passengers in a major joint exercise with U.S. counterparts to boost the country s counter-terrorism readiness. The Philippine defense ministry on Tuesday said some 1,200 uniformed and civilian Filipino and American personnel took part in the exercise  Tempest Wind  last week at a former U.S. air force base outside Manila and in Hawaii. Most of the Filipino civilian participants were not told it was a drill. The simulation was the latest exercise between the two longtime defense treaty allies at a critical time for the Philippines, which is facing its biggest internal security crisis in years as supporters of Islamic State try to gain a foothold in the south. Defence department spokesman Arsenio Andolong said civilian participants were told a plane from Sydney bound for Honolulu had been seized mid-air by eight Islamic State militants, and was making an emergency landing in Clark, north of Manila. He said the hijacking was made to appear realistic when officials from the U.S. State Department and Federal Bureau of Investigation started to provide technical intelligence about the hijackers and the flight manifest to Philippine authorities.  Many of the participants were unaware of the drill until the last minute, thinking the hijacking was for real,  Andolong told reporters. He said the operation was executed by Filipino forces guided by U.S. information and technical advice. The drill featured a negotiation phase, when Philippine authorities talked around the clock with hijackers for nearly 72 hours before commandos were sent in to  neutralize  all eight hijackers. In the scenario, some of the 182 passengers were killed.   The drill gave both sides valuable lessons on dealing with such crisis,  Andolong said.  There were many operational and tactical gaps discovered. Even the U.S. found some of its protocols did not work the way it is expected.  Militaries of both countries have for decades held training exercises in trans-national crime, disaster response and maritime security.  Washington has provided more than $700 million in security aid to the Philippines over the past 17 years. Most recently, the United States has been providing technical support to Philippine ground and air forces, who have battled for four months to retake southern Marawi City from Islamic State loyalists. The joint exercises do not, however, have the support of Philippine President Rodrigo Duterte, who has made clear his disdain for the rotating U.S. troop presence in his country during frequent tirades against the former colonial power. Defence Secretary Delfin Lorenzana said the hijacking exercise was the first of its kind involving multiple levels of security and civilian authorities.   The drill was designed to provide realistic scenarios on terrorism that demanded both high-level engagements and responses on tactical level,  he said. 