An IT glitch 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.

The departure from Birmingham Airport to the Spanish island of Majorca with 187 passengers on board was described as a “serious incident” by the Air Accidents Investigation Branch (AAIB).

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 correct figure of 69kg.

The health and safety of our customers and crew is always our primary concern. Following this isolated incident, we corrected a fault identified in our IT system

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.

Investigators described the glitch as “a simple flaw” in an IT system.

It was programmed in an unnamed foreign country where the title “Miss” is used for a child and “Ms” for an adult female.

Despite the issue, the thrust used for the departure from Birmingham on July 21 last year was only “marginally less” than it should have been, and the “safe operation of the aircraft was not compromised”, the AAIB said.

As stated in the report, the safe operation of the flight was not compromised

The same fault caused two other Tui flights to take off from the UK with inaccurate load sheets later that day.

The system was adapted when the problem was first identified 11 days earlier, but this did not correct the weight entries for the July 21 flights.

The operator subsequently introduced manual checks to ensure adult females were referred to as Ms on relevant documentation.

Tui said in a statement: “The health and safety of our customers and crew is always our primary concern.

“Following this isolated incident, we corrected a fault identified in our IT system.

“As stated in the report, the safe operation of the flight was not compromised.”