Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Mumbai to Spokane as you normally would.
BOM stands for Mumbai Chhatrapati Shivaji Intl Airport, while GEG stands for Spokane Airport. These codes are often called IATA codes, a set of identifiers established by IATA (International Air Transport Association) that is widely used by airlines and the aviation industry.