The Seed Pilot in Pikmin 4: The World to Free, is a planned machine by Captain Pikmin, that could help detect the perfect landing spot. He believes that if he made little add-on ships to the main onion, they would lower the risk of searching, and gather more info on the terrain.
The Seed Pilot plays a role in finding the first 3 Pikmin in the game, which all happened to have a problem on their way to land and got trapped somewhere. Sadly only the Seed Pilots could escape. The Seed Pilots is only available for Red, Yellow, and Blue Pikmin. And you only can carry a total of 50 Pikmin for each color. They don't appear again with you after you rescued their onion, but when Alice decides to depart on her own. She gets to bring the seed pilots with her.
Seed pilots also are run only by wireless surges. So if they lose transmission towards the onion, they power down and head back towards the onion. This means that the area you found the seed pilot is where you can only have it. However Captain Pikmin fixes this problem, so Alice could use them.