to reduce drag
Winglets increase the fuel efficiency of aircraft that have them.
Winglets are not absolutely required but many planes have winglets added to improve the aerodymanic efficiency of the wing.
Winglets increase an aircraft's operating efficiency by reducing induced drag at the tips of the wings
hanger
NO- Roosevelt had no known connection to the invention of air crafts. He did show an early interest in airplanes.
Air Canada has about 220+ Air crafts.
what are air crafts made from
Aviation fuel is a special petroleum- based fuel used to fuel jet air crafts.
Bauxite is an ore of aluminium. Aluminium is an important metal used in construction of machinery and air-crafts.
Airports
I can't think of any cathedral-wing aircraft that DO use winglets. Spanwise flow on a cathedral wing would be flowing 'uphill' (inward) and would be interrupted by the fuselage.