A network fault was to blame for thousands of passengers being left stranded at Heathrow Terminal 3 late on Thursday night.
The problems occurred at 4.30pm and left up to 6,000 passengers unable to enter the building, two flights cancelled, dozens delayed and 3,000 bags which had to be left behind. That backlog has now been cleared as systems went back online overnight.
The problem is still being investigated, but the fault appeared to lie with the network system that operates Terminal 3. Consisting of two networks, an old legacy one and a brand new one, it was thought that a device connecting them malfunctioned, creating a feedback loop.
A BAA spokesperson said: "This caused a number of systems to go down including the flight information system, CCTV, the check-in system and the baggage system.
"Parts of the network were isolated, which meant the CCTV and Check-in came back online, but it was still not communicating with the baggage system."
This meant that BAA could check-in passengers and manually tag bags but the main part of the baggage system would not accept them, which meant that other measures had to be taken which caused more disruption.
The spokesperson said that BAA were sincerely apologetic about the problems that were caused.
