Airlines association IATA said Thursday that international passenger traffic slumped 2.4 percent in April, as flight cancellations due to the volcanic ash cloud from Iceland slammed the brakes on recovery.

"The ash crisis knocked back the global recovery -- impacting carriers in all regions," said Giovanni Bisignani, director general of the International Air Transport Association.

"Last month, we were within one percent of pre-crisis traffic levels in 2008. In April, that was pushed back to seven percent," he added.

European carriers bore the brunt of the disruptions arising from the volcanic ash cloud, with traffic posted by the airlines dropping 11.7 percent in April.

Bisignani said this "could not have come at a worse time" for the region.

"Europe's slow recovery from the global financial crisis and its currency crisis are already a huge burden on the profitability of its airlines," he noted.

"The uncoordinated and excessive cancellations and unfairly onerous passenger care requirements rubbed salt into the European industry's wounds," added Bisignani, reiterating his criticism of the way European governments had handled the volcanic eruption crisis.

The impact of the ash cloud was felt beyond Europe, with North American carriers reporting a 1.9 percent decline in April demand as north Atlantic routes were also hit. This marked a sharp drop from the 7.8 percent growth posted for March.

Asia-Pacific airlines also saw their growth slow to 3.5 percent from 12.9 percent recorded in March.

Middle Eastern carriers reported growth of 13.0 percent, African carriers' traffic was up 8.6 percent while Latin American airlines recorded an increase of 1.2 percent in traffic. But all were posting significantly slower growth than in March.

Cargo traffic was meanwhile less hit by the cancellations in April, although traffic also slowed to 25.2 percent from 28.1 percent in March.

"The ash crisis was a shock. While there is always a danger of the consequences of renewed volcanic eruptions, the impact on passenger confidence should be limited," said Bisignani.

"Unfortunately, we are trading ash for two additional uncertainties -- strikes and a growing currency crisis -- both of which are also focused on Europe," he added.

He stressed that it was the wrong time for employees to ask for pay hikes or improved conditions, describing such demands as a "mentality divorced from reality."