Airports across the UK have been hit by an IT glitch on Border Force computers, resulting in extended queues at immigration desks and long delays for passengers.
As a result of the error, passport scanners stopped working, forcing UK Border Force to manually enter the details for those arriving in the UK rather than simply scanning documents.
The problem, which affected both immigration booths and e-passport queues, had a specific impact on non-EU passengers.
Several airports across the country including Heathrow, Gatwick, Birmingham, Stansted and Manchester faced the disruption.
Disruption reportedly triggered fights among queuing passengers, and extra staff were called in to try and ease the queues.
However, it has been reported today that the airports are returning to normal.
Immigration minister James Brokenshire said: "The current situation is much improved and we are doing our best to keep waiting times to a minimum during this morning's busy period.
"We apologise for any delays but security must remain our priority at all times."
A spokesman for Gatwick said the IT glitch was resolved overnight, while a Heathrow spokesman said that the passengers were clearing immigration 'in good time'.
Disruption at Britain's busiest airports on Wednesday caused long delays for the passengers, and some of them were asked to wait for around four hours.
Compuware APM VP Michael Allen said: "I got caught up in the chaos at Heathrow last night. It was crazy. Quite simply it's not acceptable for IT problems to cause this level of pain. IT systems have become more complex in recent years and it seems this complexity is increasingly leading to problems like this.
"IT teams should have the processes, techniques and tools in place to proactively avoid these problems and be equipped to deal with unexpected IT problems before they impact their users.
"They should be able to see potential problems bubbling up and deal with them before it gets to the point it did last night where thousands of us were moving at a foot a minute in the passport control queue."
Image: Several airports across the country including Heathrow, Gatwick, Birmingham, Stansted and Manchester faced the disruption. Photo: courtesy of Gatwick Airport.