Which Counter-Strike game introduced the Flying Scoutsman game mode?

Counter-Strike: Global Offensive introduced the Flying Scoutsman game mode.

Flying Scoutsman is an unusual Counter-Strike mode built around the SSG 08 sniper rifle and low-gravity movement. Players can jump farther and remain airborne longer, producing a very different style from ordinary bomb-defusal matches. The mode also uses a restricted weapon selection.

Valve added Flying Scoutsman during the Global Offensive era as part of the game’s rotating War Games content. It became one of the recognizable casual alternatives to Competitive, Casual, and Deathmatch play.

The mode is sometimes associated with Counter-Strike 2 because Counter-Strike 2 inherited much of Global Offensive’s content and terminology. Historically, however, Flying Scoutsman was introduced in Global Offensive, not in the original Counter-Strike, Source, or the later sequel.