Incident Overview
On 21 July 2020, a Boeing 737-8K5 (registration G-TAWG) operated by the UK regional arm of a large European airline departed Birmingham Airport for Palma de Mallorca, Spain, with an inaccurate load sheet. The aircraft carried 6 crew and 187 passengers; no injuries were reported and no damage occurred.
Load Sheet Discrepancy
The flight crew reviewed the flight plan, which indicated an expected takeoff weight (TOW) of 66,495 kg, and the load sheet, which gave a TOW of 64,889 kg – a difference of 1,606 kg. The load sheet showed 65 children, compared to 29 expected on the flight plan. The commander noted the high number of children but considered it plausible given recent passenger changes due to COVID-19 restrictions. The crew also observed that baggage loads included 35 bags at standard mass (16 kg) and 150 bags with actual masses averaging 14.5 kg, an unusual but permitted situation. After discussion, they accepted the load sheet.
Root Cause: IT System Flaw
The incident resulted from a programming flaw in the operator's check-in system. After an upgrade, the system interpreted the title 'Miss' as indicating a child (standard weight 35 kg) rather than an adult female (standard weight 69 kg). This misinterpretation arose because in the country where the system was programmed, 'Miss' denotes a child. Consequently, 38 adult female passengers were incorrectly classified as children, causing the load sheet to understate the actual takeoff mass by 1,244 kg.
Previous Occurrence and Mitigation
On 10 July 2020, three adult females were similarly misidentified. The operator identified the issue and manually corrected bookings by changing 'Miss' to 'Ms' for females, but this process was not applied over the weekend. Additionally, a software fix implemented on 17 July to automatically change 'Miss' to 'Ms' before check-in was being enhanced on 20 July, potentially preventing it from working. Passengers could check in online 24 hours before departure, so incorrect weights were not corrected before the incident flight.
Performance Impact
Despite the incorrect takeoff weight, calculations showed that the thrust used (88.3% N1) was marginally higher than required (88.2% N1) for the actual weight and conditions, so safe operation was not compromised. The required takeoff speeds were one knot higher than those used.
Safety Actions
Following the incident, the operator introduced a daily check to ensure adult females were listed as 'Ms' on documentation, with a secondary check by operations staff. A more formal system of checks was implemented on 24 July 2020.