A TUI flight took off heaver than expected in what was described as a “serious incident” due to an IT glitch, an investigation has found.

Thirty-eight female passengers using the title “Miss” were classified as children prior to take off.

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.

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.

The glitch was described as “a simple flaw” in an IT system by investigators.

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.

Two other TUI flights took off from the UK with inaccurate load sheets in the same day due to the same fault.

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.”