Skin discoloration can be due to changes in melanin. Melanin is a skin pigment that gives color to the skin. Changes in melanin can also cause skin to be patchy. Treatment for skin discoloration includes using topical treatments.
Winglets increase an aircraft's operating efficiency by reducing what is called induced drag at the tips of the wings. An aircraft's wing is shaped to generate negative pressure on the upper surface and positive pressure on the lower surface as the aircraft moves forward.
Other Boeing aircraft flying with winglets are the 747-400, the version currently being built, Boeing BBJ business jets which are custom-built 737s, and the C-17 military transport. Boeing is also offering winglet options on new advanced models of the 737 series of passenger jets.