An examination of North Atlantic MNPS turn-back and diversion data from 2006 through July 2009 reflects the following:

Causes of diversions and turn-backs included medical emergencies, smoke in the cockpit, fuel pressure, hydraulic problems, engine shutdown, low fuel, navigation system failure, cargo fire, generator failure and destination weather.

Diversions and turn-backs in MNPS airspace occurred at a rate of approximately 12 per month through the period.

Approximately two to three times per month, a pilot was required to use published contingency procedures to make at least the initial maneuver to start a diversion or turn-back.

“The last time that I went through the data,” a retired employee of a major aviation regulatory agency reported, “it shows that in the North Atlantic region, an emergency where an aircraft has to depart track or flight level either with or without ATC clearance occurs about 145 times per year. So, this is not uncommon.”

However, a surprising discovery that emerged from the regulator's study was the number of medical emergencies requiring a diversion to an alternate with medical facilities, usually Iceland or the Azores. “Often, this means having to turn around,” he said. “So you have to be aware that this is not uncommon where you have to move the airplane off the assigned course, either obtaining a clearance to do so, or if unable, falling back on contingency procedures designed to put the airplane where it is less likely to encounter another airplane.”

Another common diversion results from en route weather. “The other thing in the same vein, of course — a regular occurrence in the West Atlantic, Gulf of Mexico and certain areas of the Pacific — is where the aircraft has to maneuver around convective weather,” the former regulator said. “Same deal: First stipulation is to get ahold of ATC, obtain a clearance and if you can't, revert to weather deviation procedures.”

As already noted, some big changes are in the works regarding reduced separation standards on the NATS along with a commensurate avionics equipage mandate necessary to accommodate them. The precedent for this actually occurred in Pacific MNPS/OTS airspace shortly after the millennium, when lateral separation was reduced from 100 nm to 50 nm. “The standards for that are based on enhanced aircraft navigation, communication and surveillance capabilities,” the former regulator, who has played a role in developing oceanic procedures, said.

Currently, an operational trial is in progress within the Gander and Shanwick Flight Information Regions (FIRs) testing 5-min. longitudinal separation, reduced from 10 min. The trial, scheduled to run either until March 2014 or until 5-min. separation is approved by ICAO, requires equipage with GNSS, CPDLC and ADS-C with an 18-min. reporting capability — in other words, the tripartite components of FANS 1/A supporting communication, navigation and surveillance (CNS), as hammered out by ICAO signatories in the 1980s and in increasing use over both the Atlantic and Pacific oceans by the airlines and a handful of business jets.

In January 2012, a proposal to amend North Atlantic procedures in phases based on a mandate to require FANS 1/A equipage was approved by the ICAO Council. Groundwork for this will be laid with a second operational trial beginning Feb. 7, 2013, confined to two core tracks of the NATS between FL 360 and FL 390 reserved exclusively for aircraft equipped with the FANS package. On Feb. 5, 2015, this will be expanded to include so-far undetermined portions of North Atlantic MNPS airspace (outside the NATS), again only for FANS-equipped aircraft. Note that up to this point, these trials involve only equipage and not separation reductions.

Finally, lateral separation reduction from 60 nm to 25 nm by applying one-half degree spacing on the two core NATS tracks will commence with Phase 1 sometime in 2015 for FANS-equipped aircraft with RNP-4 approval. This will be followed by Phases 2 and 3, when both reduced lateral and longitudinal separation are extended, respectively, (1) throughout the entire NATS and (2) in all MNPS airspace in the North Atlantic region at dates yet to be determined (but assumed to fall before 2020).

At these points — or simultaneously, if the North Atlantic Systems Planning Group elects to implement Phases 2 and 3 at the same time, an option under consideration — all aircraft will be required to be FANS 1/A-equipped to operate on the OTS and published routes in the region.