NEW DELHI, July 14 (Reuters) - A preliminary investigation into the crash of an Air India passenger jet last month that killed 260 people raises additional questions about the incident and the investigation is far from over, Air India's CEO said in a memo on Monday.

Air India will begin operating three weekly flights between Ahmedabad and London Heathrow from August 1, replacing its existing Ahmedabad-London Gatwick service. The change comes as part of the airline's phased restoration of operations,

Air India on Tuesday said it will operate three weekly flights from Ahmedabad to Heathrow, London, from August 1 to September 30, replacing Gatwick, London.