This reasoning is extremely faulty. Do you know any airline any age that can function without an information system? Do you know any information system that is not based on a relational database? If the MySQL server in an airline's information system is down, can it function?
Or look at it this way. For the game, MySQL also "only" helps to keep track of everything. They could as well use another database system, a hand-crafted file management routine, etc. "Keeping track of everything" is essentially what a database system such as MySQL does, for both scenarios.