Cloud Nine??

"Popular etymology references the 1896 edition of the International Cloud Atlas which defined ten types of cloud. The book defined the ninth cloud as the cumulonimbus, which rises to 10 km (6.2 miles), the highest a cloud can be." No conclusive evidence, however, confirms this origin.

Or
" In Dante's Paradise, the 9th level of heaven is closest to the Divine Presence, which itself dwells at the 10th and highest heaven. This notion may have enhanced the popularity of the expression on cloud nine." No conclusive evidence, however, confirms this origin.

Or
" The true and original origin of "Cloud 9" is derived from Buddhism. The state of being in "Cloud 9" is the penultimate goal of the Bhodisattva." No conclusive evidence, however, confirms this origin.

I guess I will just stay here with my two feet planted on the ground and let my imagination soar!
Who needs to be on Cloud 9 when the view of the sky is so amazing from right here! :)