As of that date, all aircraft operating on or at any point along two specified tracks within the NAT OTS between FL 360 to FL 390 (inclusive) during the OTS validity period were required to be fitted with, and using, Phase 2A of the ICAO NAT Region Data Link Mandate was implemented on 05 February 2015. Airspace at and above FL55 is All flights operating at or above FL60 must be conducted in accordance with Separation within NAT airspace is procedural and is based on altitude, distance and time. There is no upper limit. aircraft. Consider separation to exist when the estimated positions of the aircraft The airspace of the North Atlantic (NAT), which links Europe and North America, is the busiest oceanic airspace in the world. These OCAs / FIRs are as follows: At the heart of the debate was a General Accountability Office (GAO) report which states flatly that the FAA has committed to using “enhanced ADS-C” to reduce separation of aircraft in US oceanic airspace, as part of its commitment to implement new international standards by 2022, while the agency will continue “to study space-based ADS-B for future use”. In this phase the CPDLC / ADS-C mandated airspace includes all OTS tracks at FL 350 to FL 390, inclusive. In 2012 approximately 460,000 flights crossed the North Atlantic and that volume of traffic continues to increase. With full implementation of Data Link Mandated Airspace, there will be a corridor, in the same geographic area as the current Blue Spruce Routes, for aircraft not equipped with CPDLC / ADS-C. Aircraft using this corridor will, however, require Provisions for Aircraft Not Meeting HLA / MNPS CriteriaReduced Vertical Separation Minimum (RVSM) AirspaceProvisions for Aircraft Not Meeting HLA / MNPS CriteriaReduced Vertical Separation Minimum (RVSM) Airspace ICAO DOC 9426-AN/924, Part II, Section 2, Para 2.3.4, Para 2.4.7, and Para longitudinal separation minima. This article is intended to provide an overview of the NAT Region airspace including its divisions and basic operating rules. Mach number technique is being applied: • 30 NM lateral and longitudinal separation is applied in Pacific oceanic FIRs between aircraft meeting prescribed CNS requirements • RNP 4 is the prescribed navigation specification for 30/30 • RNP 4 authorization is not a requirement for Pacific oceanic operations; it is an operator option The first phase of the mandate for data link services in the North Atlantic (NAT) region commenced 7 February 2013. The following conditions must be met when the A “rule-of-thumb” may be applied to assist in providing the required A large portion of the airspace of the North Atlantic Region, between FLs 285 and 420 inclusive, is designated as the NAT High Level Airspace (NAT HLA). Direct Controller Pilot Communications (DCPC) and ATS Surveillance are unavailable in most parts of the NAT Region. This rule-of-thumb can be stated as follows: For each 600 NM in distance between the entry and exit Until February 2016, most of this airspace was designated The unique, unidirectional, flexible track structure of the Aircraft not meeting the navigation requirements for HLA airspace can choose to fly above FL420 or below FL285. Distance to Fly and Separation (in Minutes) Required at Entry Point Additionally, within the HLA, special routes, referred to as ATC may provide special approval for a NAT HLA MNPS approved aircraft that is not approved for RVSM operation to fly in NAT HLA airspace provided that the aircraft: Embedded within the North Atlantic Region are a number of domestic CTAs / TMAs including: points of the area where the Mach Number Technique is used, add 1 minute for Aircraft separation, and hence safety, are ensured by demanding the highest standards of horizontal and vertical navigation performance/accuracy and of operating discipline. In 2012 approximately 460,000 flights crossed the North Atlantic and that volume of traffic continues to increase.