Most airlines in the US that operate the Boeing 737 NG aircraft have opted to add winglets to the end of the wings, aiding in the aircraft's fuel efficiency.

While an optional add-on for the NG aircraft, all Boeing 737 MAX 8 aircraft feature Boeing's AT winglet that resembles a V-shape on the end of each wing.

While many non-Max aircraft also feature a similar-looking add-on known as the split scimitar winglet, which also increases the aircraft's fuel efficiency, they are two different winglets. Nearly all major airlines operating the Boeing 737-800 have adopted the split scimitar, with the exception of American Airlines, making identification based on this alone slightly more difficult.