"A software mistake caused a Tui flight to take off heavier than expected as female passengers using the title 'Miss' were classified as children, an investigation has found...."

"An update to the airline’s reservation system while its planes were grounded due to the coronavirus pandemic led to 38 passengers on the flight being allocated a child’s 'standard weight' of 35kg as opposed to the adult figure of 69kg. This caused the load sheet – produced for the captain to calculate what inputs are needed for take-off – to state that the Boeing 737 was more than 1,200kg lighter than it actually was.... It was programmed in an unnamed foreign country where the title 'Miss' is used for a child and 'Ms' for an adult female." 

The Guardian reports.

69kg is 152 pounds. Think that's a good guess about what a female adult weighs? 35kg is 77 pounds. That's not that low.