Yes.

At some point prior to the merger but after 9/11, UAL ALPA decided to use the "hat switch" as a demonstration of unity and command-and-control in negotiations with the company. The union would direct pilots to either wear, or not wear, the hat as directed. Texts and emails would let pilots know the current hat position.

Since the hat was required and nearly universally worn, it was both peaceful disobedience and a display of unity.

As a result to company made the hat optional to let the air out of the balloon.