It wasn't just aircraft; this was just part of the transformation of the Locust Civilization. These insectoid beings began to develop external tools to enhance their own strength, because the extraordinary power they held in such a short time was not enough for their race to complete a civilization-wide power leap.
However, having already learned of the existence of different worlds, their desire to conquer these other worlds and acquire more resources made the upper echelons of the Locust Civilization unsatisfied with the status quo. Thus, they pushed for a transformation of their entire civilization, wanting their civilization to truly possess the power to enter the Void.