Every single day, hundreds of commercial airplanes cross the north atlantic, flying transcontinental routes linking North America and Europe basically, the NAT (North Atlantic Tracks). The performances of these flights are much different and complex due to its distant routes from any kind of airport.

The twin-engine aircrafts operating these flights (usually big ones) must have the ETOPS rating, explained in other post. That is because the nearest alternative airport when flying above the atlantic is 180 minutes far. If an engine failure happens (or any other system), this aircraft should divert to the closest airport immediately.

Another huge problem is the radar coverage. As a matter of fact, this radar coverage does not exist. Radars must be set up on ground or close (not floating over the sea). The main Air Traffic Control facilities (Shanwick Oceanic for European side and Gander Oceanic for US side) are equipped with air traffic management systems that by means of pilot manual position reports, they have some sort of “radar-like” screen with all the airplanes’ positions.

The third and big problem as well (but solved anyway) is about communications. The communicacions between pilots and controllers use VHF (Very High Frequency from 30 MHz to 300MHz) frequency range. VHF waves only reach “line-of-sight” spaces. So, in that case they must use HF (High Frequency from 3 MHz to 30MHz) that bounces off the ionosphere and give coverage to greater distances. Nevertheless, even this advantage, sound quality is much poor.

The NAT routes are designed and published daily. They are defined with an entry waypoint, an exit waypoint and between, waypoints are defined with coordinates (there are no navaids to define them). Early in the morning, westbound routes are published. Then late at night, eastbound routes are published. Europe incoming routes are usually defined at higher latitude, to take advantage of the Jet Stream (high speed wind, will post about this).
By the way, pilots flying these routes cannot eat the same meal.

Here we can appreciate North Atlantic Routes all the day long

The ETOPS (Extended-range Twin-engine Operational Performance Standards) defines the twin-engine aircrafts requirements to operate flights where the nearest enroute alternative airfield is further than 60 minutes.

At the beginning of commercial aviation, because of the lack of regulations concerning alternative airfields further than 60 minutes, the air carriers started putting pressure on Aviation Administrations to be modified,  in order to be able to operate transatlantic routes with twin-engine. Because of that, ICAO and the FAA drawn up a new reguation that allowed to operate those routes. 

Nowadays, there are several ETOPS ratings depending on some parameters. These parameters are including the engines and systems’ reliability, crew training and ratings, manteinance and so on.

Author Andrés Meneses

These are the different ETOPS ratings issued these days by Aeronautical Authorities:

• ETOPS-75
• ETOPS-90
• ETOPS-120/138 (138 minuts is a 15% plus 120 minuts, in order to cover a little part of the Atlantic Ocean, not covered with ETOPS-120)
• ETOPS-180/207

An ETOPS rating is gradual. That means if you want to reach ETOPS-120 rating, first of all the aircraft must have reached the ETOPS-75 rating (with 200 sectors with 98% relieability), then the ETOPS-90 rating (with 300 sectors with 98% reliability), and finally the ETOPS-120. For example, in order to achieve ETOPS-120 rating, the airplane must prove less than 0.05 per mil in-flight shut-down. That means, flying 20.000 flights there’s only one in-flight shut-down (obviously, an airplane does not achieve 20.000 routes in its life).

There’s a tremendous application called Great Circle Mapper where you can compute each ETOPS rating maximum range around the earth.