The momentum theorem is used to obtain the expression for the leading-edge suction force as it brings out some subtle features that are not seen when the conservation of energy is applied. The circulation distribution is elliptical and does not depend on the shape of the leading edge. The results are obtained from the theory of low aspect ratio wings by treating the crossflow past a triangular wing to be approximately two dimensional, giving the leading term in an asymptotic expansion for small aspect ratio wings.