Two U.S. pilots face a maximum of four years in jail after they were charged by a Brazilian prosecutor with "endangering air safety" in the collision between their Embraer Legacy 600 business jet and a Gol Airlines Boeing 737 in late September. However, the pilots -- Joe Lepore and Jan Paladino of New York -- were still allowed to leave Brazil on the promise that they return to face the charges. The charges were filed Friday when they appeared at a Rio de Janeiro police station to give statements. The pilots, who are now back in the U.S., have consistently denied any wrongdoing in the collision, in which a winglet on their aircraft is believed to have contacted the 737's wing, causing it to fail. All 154 people aboard the 737 died after the airliner plummeted into the Amazon jungle. Initial reports blamed the Legacy pilots, but subsequent investigations have been much less clear as to how the two aircraft, under air traffic control, ended up on a collision course at the same altitude of 37,000 feet. Among the questions raised by the investigation are why the transponder on the Legacy wasn't registering at the time of the crash and why the TCAS systems on both airplanes failed to warn of the possible collision.