Question: How many terrorists were on the second plane to hit the World Trade Center?

<P0-S0> Flight 175: As the World Watched is an American television documentary film that premiered in August 2006 on TLC. <P0-S1>  It covers the final moments of the passengers and crew on board United Airlines Flight 175, which was the second commercial airliner to strike the World Trade Center, impacted with the South Tower, and was the most visually documented (both photographed and filmed) flight during the September 11 attacks. <SEP> <P1-S0> United Airlines Flight 175 was a scheduled domestic passenger flight from Logan International Airport, in Boston, Massachusetts, to Los Angeles International Airport, in Los Angeles, California. <P1-S1>  On September 11, 2001, the Boeing 767-200 operating the route was hijacked by five al-Qaeda terrorists and flown into the South Tower of the World Trade Center in New York City, killing all 65 people aboard and an unconfirmed number in the building's impact zone. <SEP> <P2-S0> The Twin Towers of the World Trade Center collapsed on September 11, 2001, as a result of being struck by two jet airliners hijacked by 10 terrorists affiliated with al-Qaeda, during the September 11 attacks. <P2-S1>  Two of the four hijacked airliners crashed into the Twin Towers, one into the North Tower (1 World Trade Center) and the other into the South Tower (2 World Trade Center). <P2-S2>  The collapse of the Twin Towers destroyed the rest of the complex, and debris from the collapsing towers severely damaged or destroyed more than a dozen other adjacent and nearby structures. <P2-S3>  The South Tower collapsed at 9:59 am, less than an hour after being hit by the second hijacked airliner, and at 10:28 am the North Tower collapsed. <P2-S4>  Later that day, 7 World Trade Center collapsed at 5:21 pm from fires that had started when the North Tower collapsed. <P2-S5>  As a result of the attacks to the towers, a total of 2,763 people died. <P2-S6>  Of the people who died in the towers, 2,192 were civilians, 343 were firefighters, and 71 law enforcement officers. Aboard the two airplanes, 147 civilians and 10 hijackers also died. <SEP> <P3-S0> On September 11, 2001, 19 Arab-Muslim hijackers took control of four commercial aircraft and used them as suicide weapons in a series of four coordinated acts of terrorism to strike the World Trade Center in New York City, the Pentagon in Arlington County, Virginia, and an additional target in Washington, D.C. Two aircraft hit the World Trade Center while the third hit the Pentagon. <P3-S1>  However, one plane never arrived at its target; it crashed in a field in Pennsylvania because the passengers fought back. <P3-S2>  The intended target is believed to have been either the United States Capitol or the White House. <P3-S3>  As a result, 2,977 victims were killed, making it the most deadly terrorist attack on U.S. soil; also the deadliest foreign attack on U.S. soil, exceeding Japan's surprise attack on Pearl Harbor in Honolulu, Hawaii, on December 7, 1941, which killed 2,403 victims. <P3-S4>  It was carefully planned by al-Qaeda, who sent 19 terrorists to take over Boeing 757 and Boeing 767 aircraft, operated by American Airlines and United Airlines.