Float/walk on air British positive verb
Beatrice was walking on air when Patrick purposed her.
Isabelle was floating on air when she received good marks on the exam.
be so excited or nervous about that something and want to know what is going to happen next
To make someone feel more confident or happy, especially when they thought that they can't achieve what they want
Happy or cheerful; in a good mood
It is used mostly in past and present tense
I am walking on air right now because Adam has just invited me to his party
My granddad was walking on air when my mom made his favorite meal last night
(Source: Udictionaryblog)
It is uncertain about its origin as to there are many theories but this phrase is first used around the late 1800s, The earliest citation was found in the British poet John Keats in his poem Isabella, even though the orignal phrase "tread upon the air" has a slightly different form but it is similiar in meaning. They both expressed the light feeling of relief or happiness, light on your feet when you are extremely happy.