Red Coins of the Airstrip
From the Super Mario Wiki
Red Coins of the Airstrip is the second mission of the Delfino Airstrip in Super Mario Sunshine. The objective is to collect all the Red Coins around the area. This mission is only made accessible after a Pianta is paid ten coins in Delfino Plaza.
After returning to the airstrip, the player can do a Red Coin challenge. By Ground Pounding a Red Coin Switch and using the Turbo Nozzle, the player has to collect the eight Red Coins both on and around the airstrip. Collecting them all within the time limit will reward the player with the Shine Sprite.