When I toured New Zealand (6years ago) I was really struggling with this. At the time the airline policy was two items. I was flying via the USA to get most luggage allowance.
Luckily for me bike did not need to go in a bag so.
Bike to airport, turn handle bars and zip tie to cross bar. Remove rear mech, chain and pedals.
zip tie quick releases closed just in case and let air out of tyres.
I then put three of my four panniers in a bag with my tent I used a large rucksack cover. The fourth pannier I took on as hand luggage with my helmet.
At the time I didn’t encounter any problems with this solution however it really depends on the airline you are flying with.
I met people in while touring who arranged storage of a bike box while they were touring then simply repacked it to go home.
HTH
Nick