A communication error meant too many passengers at the front of a plane caused take-off issues for the pilot, air investigators found.
An Airbus A320 was replaced with an A321 ahead of a flight from London Luton Airport on January, but an email about the change was not passed on.
It meant the passenger seating plan was not adjusted to the bigger craft.
The Air Accident Investigations Branch (AAIB) said it landed safely and the operator had since taken action.
The A320 was due to be used for the flight from Luton to Prague in the Czech Republic on 16 January, but for “operational reasons” it was changed to an A321.
The Operational Control Centre (OCC) in Budapest, Hungary, sent an automated message to the Operational Handling Department (OHD) and Passenger Services Department (PSD) at Luton, but due to a “technical issue”, it was not received.
This was noticed at the 14:05 GMT and the OCC duty manager called the OHD to let them know of the change.
The details were altered in the relevant software, but the PSD was not informed and the passengers were therefore still seated in the old configuration.
When the aircraft did not respond twice to the pilot’s normal take-off commands, extra thrust was needed for it to depart safely. It landed in Prague without further incident.
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On analysing the issue the crew found the passenger distribution did not match the load sheet distribution.
An internal investigation was carried out and the AAIB said the operator took action to “highlight this event to its staff and improve their understanding of the issues raised; and improve the flow of information between operational departments when there is a change of aircraft type to reduce the risk that a similar event would occur”.
The AAIB said it would not disclose the name of the airline involved.