It was an eventful first day of operations for Terminal 5 as two major IT systems were brought down and hundreds of environmentalists staged a "flashmob" protest.

A fifth of flights have been cancelled from Heathrow Terminal 5 today, after continuing technical problems with the baggage system.

T5, which has been 15 years in planning and construction and cost £4.3 billion to build, including more than £250m in technology systems, is the first addition to Heathrow in 20 years.

Airport owner BAA called the system's problems "minor" and said they had been resolved, but the resultant flight delays and cancellations have continued into a second day.

First, British Airport Authority (BAA) was forced to stop its plans to fingerprint domestic passengers after the privacy watchdog said the move may be illegal.

Secondly, a high-tech baggage system broke down, causing up to two and a half hour baggage delays and chaos for travellers.

Nevertheless, operator BAA is determined that the terminal, entirely dedicated to British Airways (BA) flights, will use technology to help reduce the passenger congestion problems suffered by the airport’s other main terminals that are running at more than capacity. BAA said the systems are designed to streamline baggage handling and check-in, so the terminal can handle 30 million passengers per year. Passengers who have checked in online should be able to enter the terminal, drop off their bags and clear security in no more than 10 minutes, the operator has claimed.

The state-of-the-art terminal has cost BA and BAA £4.3bn to build and outfit. BA spent £75m on technology, while BAA invested a further £175m.

The technology investment is immense. T5 boasts 17 kilometres of baggage conveyor belts in a system designed to handle as many as 12,000 bags an hour. Over 400,000 man-hours have gone into developing the system's software, which has the ability to prioritise late bags. The terminal has involved 180 IT suppliers, runs 163 IT systems, manages 546 interfaces, more than 9,000 connected devices and 2,100 PCs. The building has 96 self check-in kiosks, 54 traditional check-in desks and 90 self-drop baggage depots.

Also, in preparation for T5, BA transformed its IT systems and cut operational costs.

Read our essential coverage on Terminal 5’s main IT:

Blog: Terminal Five - It happened before

Terminal 5 to put London back on map, says British Airways CIO

WLAN overcomes despair in the T5 departure lounge

BA to start Terminal 5 public trials

Lean methods drive Heathrow Terminal 5 development

BAA begins search for partner to maintain systems quality