"""to be pedantic, and yet correct.... there is no tolerance of -5+10 on a slot. this is a common misconception.
the bible on slots is the eurocontrol basic cfmu handbook. section 4 page 4-7 refers
it states quite clearly that for airline operators, they need to coordinate the departure time to comply with the slot i.e. slot time/ctot minus taxitime equals pushback time.fullstop.
the 15 minute window is designed for atc, and atc alone to " optimise the departure sequence "
pilots seem to think that this is their bit of leeway, and can get quite possesive of something that is patantly not theirs!
a little education can go a long way!
""""
Well put, and informed. the use of the extra time by pilots, instead of atc doesnt help the system function at all,along with not bothering to apply early enough for a new slot or put in a delay in order to free up that "slot" for another (in fact company) aircraft. More education on this i really do think is needed