Where are you going? Sydney? Southeast Asia?
I did DCA-PER which is 30h airtime with my kid at 13 months--although not solo.
Google layouts of your layover airports and check to see if they have playgrounds where the kid can crawl around.
Learn to do a kanga carry with a sarong--best wrap carry for walking up and down the aisles, as the kids arms are pinned in and they can't grab at things:
http://www.slingbabies.co.nz/Cache/Pictures/1665097/6_-1094957288_Kanga_carry_with_Sarong.jpg