In certain areas there is no radar so they have to follow lanes


How a commercial airliner crosses the Atlantic ocean


More here in better detail

JETSTREAM


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"Open Mike Night " sounded like a lot of fun until i found out i was going to an Autopsy

Interesting.

No radar coverage means procedural.
The beloved OTS [organised Track Structure], somewhat different to the Airways structure as we know. Some countries are doing away with their airways and moving to a "free route airspace" which gives more flexability and choice.
To fly within the OTS both crew and equipment have to meet a Minimum Navigation Performance Specification [MNPS]. If not then they fly the old Lindenburg route. You could also chose to "random track" below or above the OTS as its altitude range is FL285-FL420.

On 9/11 the OTS were heavily loaded, imaging having to sequence a turnback of all flights that hadn't reached 30W in 3-D .

Happy days shouting on HF for an oceanic clearance.

Now i wonder if the Denso nav unit meets MNPS

That was really interesting - I hadn't realised that the bulk of the Atlantic was radar free - When the Air Asia jet went missing near Australia, I assumed it was in some quiet black spot......

for those who are interested a chart depicing the MNPS area can be found at;

http://code7700.com/images/nat_mnps.png

enjoy

Interesting