Praise be to Allah.
Neither Sydney, Abu Dhabi or Bahrain is a meeqaat for Hajj or ‘Umrah, and Jeddah is not a meeqaat for people like you, rather it is a meeqaat for the people who live there.
You have to enter ihraam when you fly over the first meeqaat that you pass heading for Makkah, because the Prophet (peace and blessings of Allaah be upon him) said, when defining the meeqaats: “They are for them [their people] and for anyone who is not of their people who comes to them intending to perform Hajj and ‘Umrah.” You could ask the air stewards before you pass over them, and if you have the intention of entering into ihraam for Hajj and ‘Umrah and you recite the Talbiyah accordingly before you reach the meeqaat that you are going to pass over, lest you pass over it without entering ihraam, there is nothing wrong with that. With regard to putting on the ihraam garments, cleansing oneself or doing ghusl, that may be done in any place.
And Allaah is the Source of strength.