Half of the helicopters in the German Navy are not cleared to fly, Sueddeutsche Zeitung reports citing a document produced by Germany’s Federal Ministry of Defense.

The report comes as a response after Navy helicopter flights were suspended when the crew aboard the Luebeck frigate discovered a 20-centimeter crack in the tale of a Sea Lynx Mk88A helicopter, according to the document. Similar defects were later found on other helicopters of that type.

On August 7, helicopter flights were resumed. However, all 22 Sea Lynx Mk88A helicopters remain grounded and are undergoing further maintenance checks lasting until next year, according to the document. As a result, the fleet’s flying hours are being reduced by 75 percent.

Furthermore, two Sea Lynx Mk88A helicopters were unable to land on the Luebeck on September 18 due to ongoing maintenance. They were supposed to take part in the EU’s Operation Atalanta, which is aimed at fighting piracy off the coast of Somalia.

Sea Lynx Mk88A helicopters, in service since 1981, make up half of Germany’s rotorcraft fleet, Sueddeutsche Zeitung pointed out. Sea King helicopters make up the rest.