TWT -as far as I know, it is not. I should have been more specific. After the Air Asia accident there has been some significant changes in the filing of notifications. Many delays waiting on the tarmac for your flight plan from CGK,you have no slot and you must depart before time XX (How can you expect to depart on time when you are held as the airport is closed for "15minutes" but really 30 +.
One chestnut I heard about occurred this week -
AUS carrier requested pushback. Aircraft on 10nm final. Aircraft lands and parks at gate , AUS carrier gets pushback. Coincidence I guess.
AUS inbound from north west , 737 from CGK inbound due west. AUS slowed , vectored and made number two to 737 when AUS was 20nm + in front of 737.
But we digress ...