Heathrow's Terminal 5 will open exactly one year from today, its builders say.

Airport operator BAA says more than 90 per cent of building work is finished on the terminal which is expected to handle 30million passengers a year.

The authority is now looking for 16,000 volunteers to join six months of testing to begin in September to prove everything works, from car parking, check-in, baggage handling to computer systems and security.

BAA Heathrow chief executive officer Tony Douglas said the existing terminals were more than a third over capacity.

"Sixty-eight million passengers will fly through Heathrow this year in aging terminal facilities designed to accommodate around 45million," Mr Douglas said.

"When T5 opens and 30million passengers move out of existing terminals, for the first time we will have space to breathe in the central terminal area and have a once-in-a-lifetime opportunity to redevelop the rest of the airport and bring it up to a comparable standard to T5.

"By 2012, we aim to have either re-built or redeveloped our existing facilities and returned Heathrow to its rightful status as the world's leading international airport.

"We will be proud to welcome the world's Olympians through our gates."

British Airways will be the terminal's only occupant.

BA chief executive Willie Walsh said the new terminal would mean less queuing, faster baggage handling and better punctuality.

"The next 12 months will be extremely busy as we continue with our preparations for the move," Mr Walsh said.

The first flight to the terminal is expected to be a BA morning service from Hong Kong.

Construction of the £4.3billion terminal began in 2002.

When finished, it will be the biggest free-standing building in the UK at 40metres high, 396metres long and 176metres wide.