Gravion (2002)

The year is 2041 and the Earth’s only defense against mysterious aliens is a group of six young fighter pilots, two boys and four girls, backed by an enigmatic billionaire. The kids are serious in their mission and, although their teenage antics add humor, they always end up learning the value of friendship and teamwork - especially at the end of each episode when the battle calls for them to merge their fighters and form GRAVION, the most powerful defense and attack robot on the planet!