The US military command has grounded the Bell Boeing V-22 "Osprey" tiltrotors (airplane-helicopters). A decision taken for safety reasons, following the recent fatal plane crash involving a US Marine military aircraft, which crashed into the sea off the island of Yakushima, Japan, causing seven victims. The official announcement from Washington arrived in the last few hours.

"We have ordered the grounding to mitigate the risk while investigations continue. Information from preliminary investigations indicates that the accident was caused by a potential mechanical failure, but what caused it is currently unknown", Lieutenant General Tony Bauernfeind, head of the Air Force Special Operations Command, explained in a statement. 

This is a very important move, considering that there are approximately 400 V-22 "Ospreys" in service with the US Air Force, Navy and Marine Corps. Japan also grounded its fleet of 14 aircraft. It is not the first time that these tiltrotors have been grounded, again for safety reasons following fatal accidents. But the 20 soldiers who died in four accidents that occurred in the last 20 months give pause for thought.