HMS Ark Royal, formerly Britain's flagship aircraft carrier, sailed out of its home port on Monday to be scrapped in Turkey.

Britain, which has always prided itself on its sea power, will have to do without the ability to launch jets at sea until 2020 as it tries to balance its books and two new carriers are built.

Crowds lined the harbour walls at Portsmouth on the English south coast to say farewell to the "Mighty Ark". Some onlookers wore black armbands or waved flags.

The warship, which saw active service in the Balkans and the second war in Iraq, is being towed to Izmir on Turkey's west coast. It was sold as scrap to recycling firm Leyal, for �2.9 million ($4.4 million, 3.4 million euros).

HMS Ark Royal and its sister aircraft carriers HMS Invincible and HMS Illustrious were the biggest ships in Britain's navy -- a key part not only of Britain's defence but also its ability to project power worldwide.

Invincible was sold to Leyal for scrap in 2011, while Illustrious is serving as a helicopter landing platform and ministers hope to preserve her for the nation after it retires next year.

Britain will have no carrier strike capability until two new, bigger Queen Elizabeth Class aircraft carriers come into service from 2020.

Ark Royal sailed back into Portsmouth in December 2010 as part of eight percent defence spending cuts introduced by Prime Minister David Cameron's coalition government in a bid to shrink Britain's budget deficit.

"Ark Royal, like her sister ships, has served this country with great distinction," a Ministry of Defence spokesman told AFP.

"Retiring her five years earlier than planned was a difficult decision but it was the right one that, combined with her sale, has saved over �100 million.

"A decommissioning ceremony was held in March 2011 to pay tribute to her 31 years' service with the Royal Navy."

London decided to decommission the Ark Royal and also retire the fleet of Harrier jets deployed on board.

The Queen Elizabeth Class carriers were ordered in part because it would be more expensive to scrap pre-agreed contracts.

The government felt it could bridge the 10-year carrier gap by using foreign bases and overfly rights if required.

There have been five ships called Ark Royal, all of which were aircraft carriers except the first -- a wooden sailing ship that saw battle in 1588 in the defeat of the Spanish Armada.