UK Royal Navy aircraft carrier HMS Illustrious is undergoing sea trials after having completed a 16-month, £40m maintenance and upgrade programme.
The ship has already completed one week of initial sea safety training and preliminary sea trials, and will now undergo a further five weeks of sea trials.
The upgrade programme, undertaken by a partnership of Babcock Marine, the UK MoD and BAE Systems, is to modify the ship into a helicopter and commando carrier.
The upgrades include a fuel-efficient outer hull coating, installation of a new computer and communications system, a defensive anti-torpedo system and other improvements that lower the ship's environmental impact.
The ships will rejoin the fleet at the end of July 2011 and will then assume a helicopter and commando carrier role while HMS Ocean undergoes a planned refit.
The ship will be decommissioned following the introduction of the new Queen Elizabeth Class carriers.