I love this question! You have a brilliant imagination! Well, it is possible to power a lightbulb with a potato, so why not a plane?
What we need to think of carefully with things that fly, is how heavy they are… because the heavier the plane, the more power we need to keep it in the air. The potato produces a small voltage (or electric charge) via a chemical reaction with two dissimilar metals and the juices in the potato… so it can only really produce a very small amount of power. That means we need a mountain of potatoes! But that many potatoes will be heavy huh? So we need to keep the potatoes on the ground realistically.
Not to worry – what we could do is use the mountain of potatoes to charge a battery and then put the battery on the plane. Maybe we’re talking about a model plane here but it is possible, yes!
One thing to note though is that the reaction between the potatoes and the metal will also produce hydrogen gas (which is extremely flammable), so we’d need to keep the potato mountain away from any flames or anything that’s hot 🙂