The Boeing 767 had a Fuel Quantity Indication System (FQIS) with two redundant channels, but a design flaw caused it to fail if only one channel failed. This caused a much higher failure rate than expected. The FQIS on the aircraft had failed, and Air Canada's only spare FQIS had also failed. A technician applied a temporary workaround to the aircraft's FQIS and logged the repair, but another technician misunderstood the logbook entry and undid the repair. The Boeing 767 may not be flown with inoperative fuel gauges, but a miscommunication led the flight crew to fly using only a dripstick measurement of the fuel tanks. The crew needed to enter the fuel quantity into the flight computer in kilograms, but they mistakenly did the calculation with the density of jet fuel in pounds/litre. The aircraft ran out of fuel halfway to Edmonton, where Air Canada maintenance staff were waiting to install a working FQIS that they had borrowed from another airline.