A Greek prosecutor ordered a preliminary investigation into the accidental death of a 22-year-old British tourist decapitated from helicopter blades at the Spata heliport, East Attica, on Monday.
The pilot and two ground technicians were arrested and appeared before a public prosecutor on Monday, who released them without filing charges until a prosecutor's investigation into the causes of the fatal accident was completed.
At the heliport in Agios Georgios, the man was struck by the tail rotor while stepping off the aircraft. He and three other compatriots had just flown back from the island of Mykonos with the leased helicopter.
Ioannis Kandyllis, president of Greece's committee for aviation accidents, said Mr Fenton made his way to the helicopter's rear at a "fast pace", describing his death as "horrific".
He said instructions to stop from the crew were either missed or ignored, with the crew saying the group had initially been escorted into the lounge at the Superior Air helipad.
The rotors can spin for up to two minutes once the engine is shut off.
Mum pays tribute to 'wonderful' son
The group was to be picked up in limousines before leaving Athens on a private jet. The cost of the two helicopters is more than £15,000 ($26,000).
Mr Fenton's mother told Mail Online the family is "completely devastated".
"He was the most wonderful boy."
She says the friends were all sober and had only drunk water all day.
The group are believed to be school friends at an exclusive boarding school southeast of London. Mr Fenton attended Oxford Brookes University.