Santa Maria Oceanic — north of 27 deg. N. Lat.
New York Oceanic — North of 27 deg. N. Lat. but excluding the area west of 60 deg. W. Long. and south of 38 deg., 30 min. N. Lat.
The North Atlantic Track (NAT) Structure is a region of controlled airspace where IFR rules apply. Pilots flying the NATs are expected to use the Mach number technique to smooth the flow of traffic and enable en route step-climbing.
There are fixed airways (composite routes) in the Pacific, which are operational 24 hr. a day. These composite routes are located in U.S.-controlled oceanic/arctic airspaces called control areas (CTAs) or flight information regions (FIRs). Pursuant to the Chicago Convention, the U.S. accepted responsibility for providing ATC services over the domestic U.S. and within certain areas of the western half of the North Atlantic, the Gulf of Mexico, the Caribbean and the North Pacific. Within these CTAs/ FIRs the U.S. applies oceanic separation procedures consistent with ICAO regional procedures.
Standard ICAO oceanic procedures apply to Pacific routes, with minor differences (in spacing and separation) from those on Atlantic routes. In the Pacific, Oakland Oceanic CTA extends out to 165 deg. E. Long. (to the Tokyo CTA) and to 130 deg. E. Long. (Manila FIR). As a result, the FAA controls most of the Pacific airspace.
There are five routes that make up the North Pacific (NOPAC) routes between Alaska and Japan. The two northern routes are for westbound traffic, and the three southern routes are for eastbound flights. An organized route system, made up of six composite routes (ATS routes), is used for aircraft operating between Hawaii and the Los Angeles/San Francisco area. The routes are between FL 290 and FL 410 and use the same rules as the NOPAC routes.
Beyond approximately 200 nm from a land-based VHF communication station, HF radio is used as the main communication source for oceanic operations. A recent advance in communications technology allows reporting via satellite and communication over water via the aircraft's flight management system (FMS). This is accomplished using automatic dependent surveillance-contract (ADS-C) and controller-pilot data link communications (CPDLC). While this is the future of oceanic flight communications, currently only a few business aviation departments have this capability.
Most operators continue to use HF as their primary means of oceanic communication. The HF frequencies used en route are determined not only by the particular route flown, but also by atmospheric conditions and the time of day. Generally, lower frequencies are used during the night and higher ones during the day.
Each oceanic center has groups of HF frequencies assigned. These frequencies can be found in numerous resource locations, but most crews use the en route chart for the particular part of the world to pick up area frequencies. When receiving the oceanic clearance, the crew may request the “primary” and “secondary” HF frequencies. It is mandatory, while en route, that the primary HF be monitored.