Singapore Airlines (abbreviation: SIA or SQ) is the flag carrier of Singapore with its hub located at Changi Airport. The airline is ranked as a 5-star airline and has been ranked as the world's best airline by Skytrax five times. Singapore Airlines operates a variety of Airbus and Boeing aircraft, namely the Airbus A350-900, Airbus A380, Boeing 737 MAX 8, Boeing 747-400 Freighter, Boeing 777-300ER and Boeing 787-10. The airline has been a member of Star Alliance since April 2000.Singapore Airlines Group has more than 20 subsidiaries, including numerous airline-related subsidiaries. SIA Engineering Company handles maintenance, repair and overhaul (MRO) business across nine countries with a portfolio of 27 joint ventures including with Boeing and Rolls-Royce. Singapore Airlines Cargo operates SIA's freighter fleet and manages the cargo-hold capacity in SIA's passenger aircraft. Scoot, a wholly owned subsidiary, operates as a low-cost carrier. The airline is also notable for highlighting the Singapore Girl as its central figure in the corporate branding segment and not significantly changing its livery throughout its history.Singapore Airlines was the first to put the Airbus A380—the world's largest passenger aircraft—as well as the Boeing 787-10 into service, and is the first operator of the ultra-long-range (ULR) version of the Airbus A350-900. It ranks amongst the top 15 carriers worldwide in terms of revenue passenger kilometres and is ranked tenth in the world for international passengers carried. Singapore Airlines was voted as the Skytrax World's Best Airline Cabin Crew 2019. The airline has also won the second and fourth positions as the World's Best Airlines and World's Cleanest Airlines respectively in 2019. In 2023, the airline for the fifth time took the prize of Best Airline as well as the Best First Class Airline by Skytrax.