An underground conveyor system had become clogged up, according to the BBC's transport correspondent Tom Symonds. This was being blamed on staff failing to remove luggage quickly enough at the final unloading stage. Further technical faults also meant seven flights also had to leave T5 without luggage on board.

The opening of Heathrow Terminal 5 on March 27, 2008, is infamous in aviation history as a massive operational failure. The primary disaster involved the automated baggage handling system, which became overwhelmed within hours, leading to a backlog of over 23,000 bags and the cancellation of more than 500 flights in the first five days. The failure was attributed to a lack of "real-world" testing; while dummy runs had been done, they didn't account for the complexity of staff shifts and the high volume of live travelers. Furthermore, staff were unfamiliar with the building's layout, and the IT systems for car parking and security screening experienced significant glitches. What was meant to be a moment of national pride became a "national embarrassment," costing British Airways an estimated £16 million. Today, in 2026, the terminal is highly efficient, but its opening remains a "textbook case" for why massive infrastructure projects now require extensive, phased "soft openings" and rigorous system stress-testing.