Thickness-to-chord ratio

In order to reduce wave drag, wings should have the minimum curvature possible while still generating the required amount of lift.

The natural outcome of this requirement is a wing design that is thin and wide, which has a low thickness-to-chord ratio.

At lower speeds, undesirable parasitic drag is largely a function of the total surface area, which suggests using a wing with minimum chord, leading to the high aspect ratios seen on light aircraft and regional airliners.

For this reason, it is common for wings to taper their chord towards the tips, keeping the thickness-to-chord ratio close to constant, this also reduces induced drag at lower speeds.

The crescent wing is another solution to the design to keep a relatively constant thickness-to-chord ratio.