Which of the following is NOT a common type of aircraft configuration?

Luxury class is not a common type of aircraft configuration in the same way that the other options are categorized. Aircraft configurations typically refer to the layout and seating arrangements within an aircraft, particularly how spaces are organized to accommodate passengers and cargo.

Single aisle refers to an aircraft design with one central corridor running from the front to the back, allowing passengers to move along the row of seats easily. Twin aisle refers to a design featuring two aisles, which facilitates greater passenger capacity and often allows for more spacious seating arrangements. Economy class designates a specific passenger cabin configuration aimed at maximizing seating density, focused on affordability and functionality.

While "luxury class" might describe a high-end service level or a premium cabin experience, it does not represent a standard aircraft configuration type like single aisle, twin aisle, or economy class, which are all widely recognized terms in the aviation industry to categorically describe the physical structure of the aircraft. Hence, it stands out as not fitting the same classification criteria.