Some of the survivors of the Turkish Airlines flight which crashed in Amsterdam have returned to Istanbul. Flight TK 1951 came down in light fog while trying to land at Schipol Airport. Nine of the 134 people on board were killed. Investigators have recovered the plane’s flight recorders, which are being analysed in Paris.In total, 121 passengers required some form of hospital treatment, six are in a critical condition. Turkish Airlines maintains the aircraft underwent safety checks in line with procedures. The investigation is being led by the Dutch Safety Board, which will determine the cause of the crash, and the public prosecution office, which is investigating questions of guilt. Experts from plane-maker Boeing and investigators from the engine manufacturer, CFM International, are also assisting the Dutch authorities.