Basically it is a method for aircraft to keep separation whilst crossing the Atlantic. There is no ATC coverage or navaids so this system keeps the planes apart.


there are some special routes used for planning flights which e.g. are used
over the North Atlantic in the so-called North Atlantic Track System. This
system is a flexible route system that is redrawn every day according to the
expected winds over the North Atlantic. These routes are published by
NOTAM and are called TRACK. In a flight plan it is only necessary to advise
the entry point into the system, the track with identifier and the exit point. A
route with a track could look as follows: BURAK TRACKC YAY. This would
mean that Track C goes from BURAK to YAY as defined.
Other airways are located e.g. over the North Polar Region but are fixed.
These would belong to the PTS, the Polar Track System. There the specialty
would be that form a certain point on you need to change to TRUE TRACK
HEADINGS form the usually used magnetic heading, due to the closeness of
the magnetic pole.

I posted in a bit of a hurry and got it a bit mixed up 

Some pilots, thought are trained in Radio's so they could talk with other pilots or other people with hand radio's on the ground, not sure about range with them though, I imagine you have to be close, also I think the person taking in your position will radio it back to some airport GANDER or Shannon, or they might be where ATC is takin your position report

Quote:

Listen to this guy. As usual, he's done his homework.  
On the southern tracks there is not radar coverage beyond 180NM from either coast. That's standard LINE OF SIGHT physics. VHF communication coverage usually extends to 220-240NM from the coast. From that point on, HF is used and maintained throughout the open water portion of the flight.
Just as a reference, I have done a radio check on HF with New York while flying across the Gulf of Mexico!   Meaning: there is indeed ATC guidance the entire flight. The SELCAL that Nexus refers to is an alarm system that allows the pilot to turn off the voice of the HF. The reason this is done is to relieve the pilots of the Pop and Squeel that accompanies an HF radio. ATC alerts the crew with a SELCAL alarm when they want to communicate with a specific aircraft. The crew simply hears a two toned alarm in the cockpit(each aircraft has it's own four letter code with a different tone)and then responds normally on the HF radio.
The northern most routes are refered to as the "Blue Spruce routes" and have intemittent radar and VHF coverage. VOR guidance is provided by Goose Bay with ATC coverage by Gander. Prins Christian Sund (southern tip of Greenland)NDB provides guidance. From that point Iceland provides radar and VHF guidance until the transition to Shanwick. Quote:
So what you're saying is that the tens of thousands American spends to train each pilot on RVSM, RNP and Oceanic procedures  is completely disregarded in this situation?. mmmmm hmmmm
I would think that they would stick to ICAO 6.2. Or if they couldn't contact ATC perform a Doc 7030(standard knowledge for any pilot operating in RVSM airspace, including US domestic). I guess I need to contact Jeppesen and notify them of the error on all of there charts as well. Here I've been using the published 121.5(guard) or 123.45(air to air)all this time. I hope I don't get violated!  

As answer to the original question; this may provide a little more insight.....

http://www.faa.gov/ats/aat/IFIM