This is a track from The Bee Gees' 2001 album This Is Where I Came In, the final record released by the group before the death of Maurice Gibb in 2003.
In a 2001 interview with Mojo magazine to publicize the release of the album, Maurice Gibb enthused about some praise for this song from a certain Beach Boy. Said Gibb: "I did this song, 'Walking On Air' – very summery and Beach Boys, that wonderful type of thing – and Brian Wilson called me last night and said, 'I'm blown away with 'Walking On Air'.' Which just validated it for me, because it was like a tribute to him, because of all the harmonies they've done over the years which influenced so many people, particularly us." (This interview is available at Rock's Backpages.)