the aircraft. The pilots heard a popping sound around 18:51, during dinner service, and discovered that the lavatory's circuit breakers had tripped. Captain Cameron's initial attempt to reset the circuit breakers was unsuccessful. It was not uncommon for a plane's lavatory circuits to pop occasionally, precipitated by a large number of passengers using the toilet after eating, so Cameron waited around eight minutes to give the tripped circuits time to cool down before attempting to reset them again at 18:59. The captain observed that the circuit breakers popped back out as he pushed them to reset. At about 19:00, a passenger seated in the last row informed flight attendant Judi Davidson of a strange odour in the rear of the airplane. Davidson traced the odour to the aft lavatory. Davidson attempted to check on the lavatory by opening the door a few inches. At that time she observed the lavatory full of light grey smoke, but did not see flames. Davidson asked flight attendant Laura Kayama to find chief flight attendant Sergio Benetti, who entered the lavatory to investigate. Benetti saw no flames, but did see curls of thick black smoke coming out from the seams around the walls of the lavatory. While Benetti sprayed the interior of the lavatory with a CO2 fire extinguisher, Kayama moved passengers on the sparsely-populated flight forward, and opened air vents to let more fresh air into the cabin. Kayama also went to the cockpit, and at 19:02, informed the flight crew of a "fire in the washroom". Captain Cameron put on his oxygen mask and ordered First Officer Ouimet to go back and investigate. Ouimet found that thick smoke was filling the last three to four rows of seats, and he could not reach the aft lavatory. Benetti informed Ouimet that he did not see the source of the fire, but had doused the lavatory with fire retardant. Benetti told Ouimet that he did not believe the fire was in the trash bin. At 19:04, Ouimet returned to the cockpit, told Cameron about the smoke, and suggested descending. However, Ouimet did not report Benetti's comment that the fire was not a mere trash bin fire. A few seconds later, Benetti came to the cockpit and told the captain that passengers were moved forward and that the smoke was "easing up." Cameron sent Ouimet back to try inspecting the aft lavatory again. At 19:06,