Good posts there 'tready':-)
An Eg of why the system can't work properly sometimes due too many variables.
4 sector day. ML-BN-ML-SY-ML. COBT ML xxxx, A/C just gets away off Chocks at COBT+15 say due slow boarding hassles. 30 mins to get airborne due single Rwy Ops ML in the peak times (this is very common & the favored the 'sky Gods' don't help either!). Peak Hld time into BN +40 mins . So that's a possible 85mins total so far before you land, well behind Sched already.
Launch out of BN to ML +15 of COBT (due whatever reason you can think of there are zillions with aviation!) En-route slow down/hold due all sorts of reasons.Say typical 15mins, that's now 100 mins or so behind the 8 ball & then the whole ball game gets even uglier due the other COBT's for both the other two planned sectors Syd & back to ML are long gone out the window.
All of the above is very real & it doesn't inc WX into the mix.
OTP is a commercial tool for selling tickets, might as well shred that as nobody will ever achieve anywhere near their OTP times here in Oz, just not possible whilst we build more car parks the rest of the advanced world build more Rwy's/Dromes
Wmk2