when delta increase its average fares, american airlines and united often follow with similar increases. this is an example of

This is an example of status quo pricing.

Explanation:

Status quo refers to following an already established and existing way of something. It is mostly regarding social norms.

Satus quo pricing is a strategy used by companies in which one copies or maintains similar price levels as the market or as the company's competitors. It is a strategy used generally when the companies don't want to move things around, maintaining the industry's status quo.