A teenager has admitted to making bogus bomb threats that triggered the evacuation of more than 400 UK schools.
George Duke-Cohan twice targeted schools in the UK and US with hoax messages – including ones in Hampshire.
The 19-year-old of Mutchetts Close, Watford, also phoned in a fake report of a hijacked aircraft while under investigation.
He pleaded guilty to three counts of making hoax bomb threats, during a hearing at Luton Magistrates' Court yesterday (September 3), the National Crime Agency (NCA) said.
Duke-Cohan had first created panic in March 2018 when he emailed thousands of schools in the UK warning about an explosive.
More than 400 schools were evacuated as a result, and he was arrested just days later.
But despite being under investigation, in April he send another batch of emails to schools in the US and UK while under investigation claiming that pipe bombs had been planted on the premises.
Duke-Cohan was arrested for a second time and released on pre-charge bail with conditions that he did not use electronic devices.
Before long his name was in the frame for a third hoax - regarding a bogus tip-off that hijackers had taken over a United Airlines flight between UK and San Francisco.
A joint investigation between the NCA and the FBI was launched when a hacker group known as "Apophis Squad" claimed on social media that it had successfully grounded flight UAL 949 on August 9.
Detectives found that Duke-Cohan had made the calls to San Francisco Airport and their police force while he was on pre-charge bail for the two previous offences.
He posed as a worried father, claiming his daughter had contacted him from the flight to say her plane had been hijacked by gunmen with a bomb.
The plane was placed on lockdown when it arrived at San Francisco airport as the report was investigated, requiring all 295 passengers to remain on board.
This caused disruption to onward journeys and financial loss to the airline.
Duke-Cohan was arrested for a third time at his home in Watford, Hertfordshire, on Friday (August 31).
He was found to be in possession of numerous electronic devices, despite the restrictions in place .
The teenager was remanded in custody after his guilty plea and is due to appear at Luton Crown Court on September 21.
NCA senior investigating officer Marc Horsfall said: ‘George Duke-Cohan made a series of bomb threats that caused serious worry and inconvenience to thousands of people, not least an international airline.
‘He carried out these threats hidden behind a computer screen for his own enjoyment, with no consideration for the effect he was having on others.
'Despite being arrested and having conditions imposed restricting his use of technology, he persistently broke those conditions to continue his wave of violent threats.’