The man who caused a Hurghada-bound Polish plane to perform an emergency landing in Burgas, Bulgaria and admitted to having joked about a bomb on board may be sentenced to up to 15 years in prison, Bulgarian authorities say.

Prosecutor Lyubomir Petrov is quoted by Focus News Agency as saying the man, 67, would be indicted under Article 341A (2) of Bulgaria's Criminal Code for having put in danger the security of Bulgaria's airspace.

The man has been detained for 72 hours. As many as 7 witnesses have been questioned, with interrogation still ongoing.

The crew on board the Smart Planet Airlines flight took his "joke" seriously and forced landing followed suit.

A terror attack at the Sarafovo airport in Burgas killed in 2012 five Israeli tourists and a Bulgarian bus driver.

Thursday's development also comes days after Russian authorities announced the Kogalymavia airplane that crashed in the Sinai peninsula en route to Sharm El Sheikh (also in Egypt), killing all 224 on board, had been downed by a homemade bomb.

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