The objective of this work is to modify the wing of the Unmanned Airplane of Ecological Conservation adding wing twist in order to reduce induced drag at a design lift coefficient using a method based on the lifting–line theory, and test such modification using two different three-dimensional panel method codes. The aircraft is a small airplane designed to make daily patrols over petroleum extraction zones. A linear washout distribution between the boom and the wing tip was chosen for the ANCE wing. The optimum twist angle at a design lift coefficient was calculated, resulting in 5.4119 deg. The resultant induced drag reduction for the wing at design lift coefficient is equal to 6.425%. The panel method codes PAN AIR and CMARC were used to study the inviscid aerodynamic flowfield around the aircraft. The results show that the addition of wing twist increases the lift–drag ratio 2.03% and 1.53% respect to the original, when it is computed using PAN AIR and CMARC, respectively, assuming that the wing twist does not change the viscous drag. The lift coefficient at zero angle of attack was reduced by wing twist addition and the lift slope is independent of twist.