MOSCOW (AP) — Christophe de Margerie, the charismatic CEO of Total SA who helped establish the multinational oil company as one of the world’s biggest, was killed at a Moscow airport when his private jet collided with a snowplow whose driver was reportedly drunk.

As well as questioning the driver, Russian investigators said Tuesday they were also assessing whether any mistakes were made by air traffic controllers in the crash which also killed three French crew members.