We have developed an autopilot, called LORA III, which is inspired by motion vision in flying insects. It incorporates two interdependent optic flow (OF) regulators, each of which controls one translational degree of freedom: a bilateral OF regulator controls the robot's speed automatically, while a unilateral OF regulator makes the robot avoid lateral obstacles. A fully actuated hovercraft is simulated, and the results show that it is able to cross a tapered corridor. The robot requires only a pair of lateral eyes that measure the right and left OFs. This minimalistic visual guidance system suffices to control both speed and clearance from obstacles automatically, without requiring any speed and range sensors. LORA III is a first step toward a low-cost, lightweight, and power-lean guidance system for micro-air vehicles. LORA III also allowed us to reconsider the "OF balance" hypothesis that was proposed 20 years ago to explain honeybees' "centering behaviour" in a corridor.