Or more accurately, the Flower Duet from the opera Lakmé, by Léo Delibes...
Air New Zealand used to use Pokarekare Ana (a Maori song from the early 20th century), and before that Bette Midler's Wind Beneath My Wings
During their union, Air New Zealand and Ansett Australia used Vanessa Amorosi's Shine (kind of ironic when you consider it was a song about suicide, and that their slogan of 'Absolutely' would have fitted well with another Amorosi song...)
Qantas are well known for using I Still Call Australia Home, which was originally sung by Peter Allen. The Qantas version is sung by a children's choir, and interestingly, 'Rio', where Qantas didn't fly, was replaced by 'Rome', where they flew at the time of the campaign first starting, but no longer do...
Ansett New Zealand, when they existed, used a Mozart piece (the name of which escapes me at the moment), and later on High by Lighthouse Family.
"So powerful is the light of unity that it can illuminate the whole earth." - Bahá'u'lláh