The word "flier" refers to a person or object that flies, like a bird or an airplane. It can also mean a small piece of paper with information on it that people hand out or post to advertise something. Full definition
Dear Cashing In, Last week, my nephew posted on Facebook that he and his fiancee have created a gift registry for frequent flier miles for their wedding this fall. (creditcards.com)
A multi-trip travel insurance is a type of travel insurance offering extended coverage usually for a year, specially designed for frequent fliers for multiple trips so that they don't have to apply for insurance every time they travel. (policybazaar.com)