FRANKFURT (Reuters) - Germany's top airlines renewed their criticism of how air traffic authorities are handling airspace closures, after they halted flights in southern Germany for hours on Sunday, saying volcanic ash posed a risk to safety.
German air traffic control body DFS halted flights to and from Munich, Stuttgart and some other airports on Sunday based on forecasts for the ash cloud's path from London's Volcanic Ash Advisory Centre (VAAC).
German flagship Lufthansa and Air Berlin, the country's No.2 carrier, said separately on Monday it did not make sense to shut airspace in southern Germany and northern Italy based on data from London while nearby Switzerland kept its airspace open after conducting its own measurements.
Lufthansa spokesman Klaus Walther said Sunday's airspace closure may have been entirely unnecessary.
"We are demanding concrete measurements," Walther said.
Air Berlin said there was insufficient reason to close the skies on Sunday.
"There is no verified data," Air Berlin spokesman Hans-Christoph Noack said.
The spread of ash from an erupting volcano under the Eyjafjallajokull glacier in Iceland grounded much of European air traffic for nearly a week last month and a continued spray of ash has led to intermittent disruptions since then.
Airlines had to cancel around 100,000 flights in April, stranding millions of passengers. The International Air Transport Association (IATA) said airlines lost more than $1.7 billion (1.13 billion pounds) in revenue due to the volcano.
Lufthansa and fellow European airlines bundled by industry body Association of European Airlines will seek compensation for damages due to the volcano crisis, Lufthansa's Walther said.
"There is an immense damage to airlines," he said.
Volcanic ash is abrasive and can strip off aerodynamic surfaces on aircraft and paralyse engines as well as damaging electronics and windshields.
Air Berlin carried 16.5 percent fewer passengers in April than a year earlier. Larger carriers British Airways and Air France-KLM posted declines exceeding 20 percent. Lufthansa is due to publish April traffic figures on Tuesday.
Lufthansa has already said it lost almost 200 million euros (178.8 million pounds) due to ash-related airspace closures in April, which will be reflected in its second-quarter earnings.
The impact of airspace closures in April and this month was also felt outside of Europe. China Southern Airline cancelled a flight from Guangzhou to Paris on Sunday and postponed service from Shanghai to Frankfurt on Monday.
(Reporting by Maria Sheahan; editing by Karen Foster)