HMS Queen Elizabeth, which weighs 65,000 tonnes, made its way under the iconic bridge in Scotland just before midnight.
Crowds of people had gathered to watch it go underneath the bridge after it had set sail for the first time.
But last night there were fears the giant aircraft carrier could be vulnerable to a cyber-attack.
Navy chiefs boasted the defence system on the UK’s biggest ever warship, the HMS Queen Elizabeth, will be NASA standard – rather than like the NHS system that was hacked into several months ago.
But computers in the flying control room on the £3.1billion state-of-the-art carrier showed the system was still running on Windows XP.
This was the same software used by the NHS computers which were hit by a global cyber-attack in May this year.
The operating system was released in 2001, and Microsoft cut support for it in 2014. Microsoft no longer distributes security updates for XP, leaving it vulnerable to viruses and cyber-criminals.
Experts warned those still running the software after 2014 – and not receiving extended security support – are at risk of getting hacked.
Fears were growing on the same day Britain’s biggest ever warship set sail for the first time – with the Russians watching – in a historic moment for the Royal Navy.
Measuring 280-metres long, it is so large its captain described it as the UK’s new ‘sea base’ – which will take the fight to any adversaries across the globe.