Giovanni Bisignani, head of the International Air Transport Association (IATA) has said that the hard conditions suffered by airlines hit by the global downturn were improving but that the road to recovery will be long, AFP has reported. The aviation industry had forecast a worldwide drop in revenues of $80bn, from $535bn in 2008 to $455bn in 2009, he said. 'A drop of this dimension will not be easy to address. It will take three or four years to return to the old levels,' he noted.