The 24-year-old was reported to have been "shaking violently" when he bit a male passenger who was sitting near him on the short flight from Lisbon, Portugal to Dublin.
Cabin crew were reportedly trying to restrain the man when he lost consciousness and subsequently died.
New reports now suggest the bizzare death may have been a result of drug trafficking.
According to reports in RTE News a number of packages were removed from the man`s body during a post mortem examination.
The packages have been sent for forensic analysis.
A 44-year-old woman, who was also on the flight, has been arrested. According to British media reports, the Portuguese woman`s bags were searched and a quantity of amphetamines were discovered.
John Leonard, one of the passengers on the flight, told Irish radio that the man had suffered a "very violent end".
"The noise he was making was like something I have never heard before. Deep anguish is the best way I could describe it - very, very troubled. Just a very guttural [sound] from deep within him.
"To die that way in the back of an aeroplane, it`s not right," he said. "It was not very pleasant at all."
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