United Airlines
United Airlines provides flights from Romulus to Denver with the minimum price per 1 adult round-trip ticket of $272 and San Francisco with the minimum price per 1 adult round-trip ticket of $831, and seasonal flights to Chicago with the minimum price per 1 adult round-trip ticket of $339, Houston for $285, Newark for $417. The prices for tickets were taken from the official website and are indicated for October-December 2018.
Phone number: +1-800-864-8331
Official Website: https://www.united.com/en/us/