Hold on a sec, the distinction is between an overhead cost and a plain cost. An overhead cost being a cost not related to the provision of service.
https://www.investopedia.com/terms/o/overhead.aspWhat is Overhead?
Overhead includes all ongoing
business expenses not including or related to direct labor or direct materials used in creating a product or service. A company must pay overhead on an ongoing basis, regardless of how much or how little the company is selling. It is important for budgeting purposes, but also for determining how much a company must charge for its products or services to make a profit. For example, a service-based business with an office has overhead expenses, such as rent, utilities, and
insurance that are in addition to direct costs of providing its service. Overhead is any expense that supports the making or selling of a product or service.
IT is no longer an overhead cost for airlines (and hasn't been for some long time). As we see with these outages, airlines cease to fly with certain types of IT outage.
"Disclaimer, strategist and executive education tutor in a business school here - I am surprised that you misdescribe an overhead and some other definitions.
Identifying IT as an overhead is not an attitude, it is a fact"
It is not a fact, it is a mistake. Accountancy needs to put away its quill and amble into the late 19th century.