As far as I remember (somebody please correct me if I'm talking rubbish...)
If the route which has been programmed into the Flight Management Computer (FMC) includes the arrival at the destination (sometimes it doesn't - on several 767 trips back from the Indian Ocean our FMC got filled up and we got a "Route Full" message, so we had to delay putting in the arrival into Gatwick until a quiet point in the cruise when the route had freed up enough waypoints to give us space), and...
if the arrival at the destination includes a hold, or if the missed approach ends in a hold, and...
the route has been activated, and...
the autopilot is in Lateral navigation (LNAV) mode, then
the autopilot should fly the aircraft along the magenta line on the nav screen and enter any hold which it encounters. If you reach the end of the route without meeting a hold, the autopilot will go from LNAV mode to HDG HOLD mode and fly off into the distance on the last heading. Twiddling the heading knob has no effect - you need to press it in to activate HDG SEL mode and then you can drive it round using just finger and thumb.
(it would be just our luck for the aircraft to be on a radar heading when the PPL gets to the flight deck, then it won't hold or follow the route until you fiddle with the heading button)
In vertical terms, as you approach the point where the FMC has calculated you should start down, you'll get a message "RESET MCP ALT" message to remind you. If you dial in a lower altitude in the Mode Control Panel then the aircraft will start down by itself. If you don't then if I remember correctly the autopilot goes from Vertical Navigation (VNAV) to Altitude Hold (ALT HOLD).
In ALT HOLD you'll need to control speed using the MCP speed window, which in VNAV was blank. Trouble is, this opens in IAS and needs to be selected to MACH at high level using the wee button underneath it. If you don't the autothrust will maintain IAS and any changes in temperature outside (not uncommon) will change the local speed of sound and thus the Mach No. for our IAS. If we are high with a small margin between too slow and too fast (the aforementioned "coffin corner") then the automatics could either (less likely due to stick shakers, pushers etc) stall the aircraft (leading to a "Jet Upset") or more likely exceed Mach Crit (leading to "Mach tuck"), with all the attendant warnings, alarms and general doom.
Awww cr*p I've rambled on again. To answer your question...the automatics will follow the programmed route if the route is active and LNAV is engaged (unless [here we go again!] you were on a heading which diverged from the route, then if you press the LNAV button all that'll happen is a message saying "NOT ON INTERCEPT HEADING"). If there's an active hold in the programmed route the aircraft will enter and hold until the fuel runs out, if you let it.
For vertical profile the aircraft (Boeing) will happily fly the whole route at cruise level, overflying the runway down the centreline at (e.g) FL350. I did hear that an Airbus Flight Management and Guidance System (FMGS) has a different philosophy whereby the aircraft will start down automatically unless you select an altitude hold mode. But that could be total bolleaux, somebody else can advise.
The manuals you'll find in the "ship's library" behind the First Officers seat (Boeing). It would probably take too long to find the relevant page so....The PTT is on the forward side of the yoke (out of view) at the top of one of the horns and is a rocker switch - UP (spring loaded) - PTT on the radio, centre and DOWN (not spring loaded) for intercom. Plus one for each pilot on the centre console by the volume controls, plus one for each pilot on the glareshield as well, outboard of the MCP. Some older Boeings don't have the glareshield PTTs fitted.
I need my medical back soon, I'm spending far too much time at the keyboard!
