Delfino Airstrip

The Delfino Airstrip is a seaside location where tourists first come to when visiting Isle Delfino by plane. It is a simple landing strip built on small islets in the waters near Delfino Plaza. Travelers can reach the mainland via small boats.

Super Mario Sunshine
When Mario, Princess Peach, and Toadsworth landed here, the plane almost crashed since Goop was smack in the middle of the airstrip. When Toadsworth asked Mario to gather information about the situation, he instead found F.L.U.D.D., who proved to be invaluable in getting rid of the Goop. Peach also sees Shadow Mario at the airstrip. Mario and F.L.U.D.D. then started squirting the Goop until all that was left was the center, which couldn't be cleaned away as easily. Out came a huge Polluted Piranha Plant, which Mario had to defeat by squirting into its open mouth three times with F.L.U.D.D. When the plant was beaten, all the Goop cleared away, the shining center platform rose, and out came a Shine Sprite.

It wasn't until Mario defeated Bowser and Bowser Jr. that he would have come back to the Airstrip. There he would collect Red Coins and earn another Shine Sprite. Also, when he came back to the Airstrip it was covered with Strollin' Stus. Alternatively, it is possible for Mario to visit the Airstrip before defeating Bowser - the player simply has to enter Corona Mountain and leave again, and the boat to the Airstrip will be available. To get on the boat, a Pianta will ask the player to pay him ten Coins, or else he can't ride on the boat to the Airstrip.

Super Smash Bros. Brawl
Delfino Airstrip only makes a tiny cameo in Super Smash Bros. Brawl in the background of the Delfino Plaza stage. Surprisingly enough, the airstrip's model seems to be largely simplified from its appearance in Super Mario Sunshine, in that it simply looks like a floating block in the ocean.

Official Description
''A simple airstrip built on small islets in the waters near Delfino Plaza. Access to the mainland is via small boats.''

Trivia

 * After beating the game and going back to the airstrip, as a glitch the Guide Book will display Mario's location as being in Delfino Plaza.
 * The music heard the first time the player is in the airstrip is a mysterious remix of the original 'Underground BGM' music from Super Mario Bros.. When the player returns to the airstrip, the Delfino Plaza music plays instead.
 * The Goop in the center of the airstrip is in the shape of Mario's face. One can make out the mustache and the hat with the signature "M" on it. (See above)