High-speed
At higher speeds nearing the speed of sound, a new form of drag appears: wave drag. Wave drag is considerably more powerful than induced drag, and must be avoided at all costs to improve performance. Doing so demands a wing that is as thin as possible, with a slowly changing profile over a wide chord. Of course, this is basically the opposite goal to low speed wings, which presents a problem.
Just as on the lower speed designs, making an ideal high speed planform is difficult for practical reasons. In this case, a very thin wing makes it difficult to use the internal room to store fuel and landing gear, makes the wing far less stiff torsionally, and causes increased induced drag when flying slower.
Solutions to this problem come in many forms, notably the use of the swept wing and delta wing, both of which avoid the shock wave at the leading edge. Other designs make the wing as thin as possible, leading to designs like the F-104 Starfighter.
Read more about this topic: Planform