 On very small aircraft such as the Beechcraft 1900 there are only individual seats on each side of the aisle (1+1 seating).The widest narrow body aircraft such as the Airbus A320 family and Boeing 737 aircraft have six abreast seating in a 3+3 layout.Asymmetrical layouts also exist, examples including the Embraer Regional Jet which has 1+2 seating while the Douglas DC-9 and Sukhoi Superjet 100 aircraft typically feature 2+3 seating.