I am following Air Canada 873 EDDF to CYYZ and, normally, it follows a NAT. Just now, it doesn't look as if it has followed any of the NATs but has travelled about 500 nm further north than the present NATA. Since, I understand, the NATs are chosen as the most fuel efficient routes, what could be the reason for going so much further north?

 

As an afterthought, is it possible that NATA was that much further north when the flight started but has since been adjusted southwards? Can it change that much in approximately 6 hours?

Hey Dugald ,

 

What are you using to track the flight and compliance with the assigned NAT?

 

Using Flight Aware, I wasn't able to see the large deviation of the flight you referred to, however I am seeing the same thing with BAW219.

I have no idea why the deviation between Planned and Actual Flight Plans, unless maybe the flight plan was changed?

 

It's a VERY interesting observation what will no doubt lead to me learning more about this.  Looking forward to someone helping to figure out what this is.

 

Thanks for the post!

Mostly, I'm looking at Flight Radar 24 and comparing with the current NATs at SkyVector. Also, FlightAware shows a partial route 6600N 05000W CLAVY CLAVY IKMAN JELCO VANSI YXI IMEBA2. SkyVector shows NATA exiting at PIDSO just now but I don't know what it was earlier.

There are several area's in Canada's north and over the Atlandtic where the aircraft is out of radar contact. One area in particular is over Hudson's Bay. The aircraft doesn't disappear from the NAT on screen as the computer updates it's location based on heading and speed. When the aircraft has a radar hit once again the aircraft can jump to its actual location, I heard that in some areas the aircraft can be out of radar contact for up to an hour. 

 

Also an aircraft requesting a different speed or altitude then assingned the aircraft may move off track and fly a course parallel to the track

What we call these routing options are "Non Standard Tracks", these are used mainly for several reasons:

1: The jet-stream winds (Blowing from the US to Europe) would be strong enough to warrant a non standard track that would save time and/or fuel.

 

2: The company or flight crew feel that due to traffic (remember, the NAT system is like a rail road system with each leg between the Co-ordinates acting as blocks, at each         altitude only a set number of aircraft may enter a block at intervals, report leaving a block before another number or aircraft will be allowed to enter the block) or airspace         restrictions at any time during the flight, use of a standard NAT would mean a diversion off route or delay on departure or arrival which would cause longer delays.

 

3: The route of a non standard track may be the best viable option for any possible weather avoidance, if you can avoid heavy turbulence or icing conditions at your planned       altitude before departure, a re-routing may be a safer option.

 

4: Arrival times, these are heavily restricted at major airports at peak times due to gate/stand availabilities, a slightly longer route may be required if the planned ETA is (within     a certain time restriction) earlier than planned, the only other option beside this is if two flights operate the same route and the company aircraft is slightly delayed, they can     swap the aircraft callsign to the flight number that is expected to arrive earlier, but this can only be done if both aircraft are on the ground and with Dispatch & ATC                   approval.

 

There are other reasons that flights may operate on a non standard track, but these tend to be the most common

Number 2 seems the most likely since the flight did not pass over the UK as it usually does but went straight up the North Sea to the Shetland Islands and over the north tip of Iceland. The UK airspace looked particularly congested.