For a drone attack to have knocked half of its - and 5% of the world's - oil supply offline, speaks to the vulnerability of their plants and in turn to the vulnerability of a vital part of the global energy infrastructure.
The Khurais oilfield produces about 1% of the world's oil, and Abqaiq is the company's largest facility - with the capacity to process 7% of the global supply.
Questions being asked centre on why this attack could not have been prevented by a company with such deep pockets and whether it can happen again.
