This is why airplanes and volcanic ash and dust don't mix:
On June 24th, 1982, a British Airways 009, Boeing 747-236B G-BDXH (cn 21635/365) "City of Edinburgh", was enroute to Perth, Australia, when it flew into a cloud of volcanic ash and dust. The result was heavy damage to the airframe and flame-out of all four engines. The crew was able to restart the engines and land safely in Jakarta."The result of a forensic investigation into the incident was to change pilot training around the world. Engineers at Rolls-Royce found that the engines had seized up because the plane had flown through a cloud of volcanic ash."
Below is a photo of the aircraft involved, Boeing 747-236B G-BDXH (cn 21635/365) "City of Edinburgh". After the incident, she was repaired and returned to service.