British-Indian student Aditya Verma is currently undergoing trial in Spain for a message he sent to friends during a trip to Menorca in July 2022.
In the message, Verma humorously claimed to be a "member of Taliban" heading to blow up a plane.
Although not facing terrorism charges or imprisonment, he could potentially be fined 22,500 euros if found guilty.
UK security services intercepted the message on the Gatwick Wi-Fi network and reported it to Spanish police while the easyJet plane was in flight.
During the trial in a Madrid court, Verma clarified that his intention was not to harm or distress the public. Spanish F-18 fighter jets were deployed in response to the alarming message, with one jet tailing the aircraft until it safely landed in Menorca for thorough inspection.
The 18-year-old Verma spent two days in a police cell before being released on bail.
Subsequently, he was questioned by British intelligence services MI5 and MI6 in the UK and returned to Orpington, Kent.
During the trial, Verma on Monday said the message was "a joke in a private group setting". "It was just sent to my friends I was travelling with on the day," he was quoted as saying by the BBC.
When asked about the reason for sending the message, Verma replied, "Since school, it's been a joke because of my features... It was just to make people laugh."
Responding to another query about when he saw the Spanish fighter jets flanking his plane, Verma believed that it was a military exercise related to the Russia-Ukraine war.
Police informed the court that they searched Verma's phone and found he researched clashes between India and Pakistan and the possibility of an attack by the Islamic State terror group in that area. However, the officials did not find any related link between Verma and jihadist radicalism.
The Spanish Defence Ministry is demanding 95,000 euros (Rs 85.94 lakh) in expenses in Verma's case.
A verdict in Verma's case is expected in the next few days, the court told the BBC.
