Bomb threats against passenger aircraft continue in Europe, APA reports.
The number of aircraft targeted by such threats has risen to 21.
Bomb threats have been received against aircraft operating flights to Madrid, Rome, Prague, Belgrade and other cities.
No explosives were found during inspections of the aircraft.
A group calling itself "Warriors of the Male State" has claimed responsibility for some of the threats in Italy.
The group issued threats of explosions in a message sent via email.