There could be multiple reasons why it was delayed 20 hours:
- A no dispatch MEL
-Crew called in unfit for duty
For the former, parts are not readily available and needs time to get from Seattle to Perth, and 20 hours is considered lightening fast considering it’s about 2 hours from SEA to LAX/SFO then another 15.5 hours to SYD and 4.5 hours to PER, including transit and handling, I think that’s quick!