In older aircraft that flew with a three-person crew, the flight engineer kept a fuel log and supervised the fueling. The Boeing 767 belonged to a new generation of aircraft that flew with only a pilot and co-pilot, but Air Canada had not clearly assigned responsibility for supervising the fueling. On the day of the accident, two technicians and two pilots worked on the calculation in Montreal. One technician stopped after he found that he wasn't making any progress. Another technician was using a piece of paper that he had in his pocket, and he stopped when he ran out of space. First Office Quintal did the calculation by hand, and Captain Pearson checked the arithmetic with his Jeppesen slide rule.