Grid fins are used on the Falcon 9 rocket for increased precision and accuracy in control of the landing location for reusable launch vehicles. It therefore helps the rocket to land on the landing pad or Autonomous spaceport drone ship more precisely with good accuracy. The grid fin development effort is a part of the SpaceX reusable launch system development program that has been underway since 2012. The first hypersonic flight test with grid fins was in February 2015, and grid fins were subsequently used on all reusable Falcon 9 experimental test landings and, eventually, after December 2015, an increasing number of successful first stage landings and recoveries.