Aeronautical Information ManualChange 3 · Effective 7/9/2026
Chapter 4 · Section 7
Operational Policy/Procedures for the Gulf of America 50 NM Lateral Separation Initiative
6 Paragraphs4-7-1–4-7-6
4-7-1 Introduction and General Policies
Air traffic control (ATC) may apply 50 nautical mile (NM) lateral separation (i.e., lateral spacing) between airplanes authorized for Required Navigation Performance (RNP) 10 or RNP 4 operating in the Gulf of America. 50 NM lateral separation may be applied in the following airspace:
Houston Oceanic Control Area (CTA)/Flight Information Region (FIR).
Gulf of America portion of the Miami Oceanic CTA/FIR.
Monterrey CTA.
Merida High CTA within the Mexico CTA/FIR.
Within the Gulf of America airspace described above, pairs of airplanes whose flight plans indicate approval for PBN and either RNP 10 or RNP 4 may be spaced by ATC at lateral intervals of 50 NM. ATC will space any airplane without RNP 10 or RNP 4 capability such that at least 90 NM lateral separation is maintained with other airplanes in the Miami Oceanic CTA/FIR, and at least 100 NM separation is maintained in the Houston, Monterrey, and Merida CTA/FIRs.
The reduced lateral separation allows more airplanes to fly on optimum routes/altitudes over the Gulf of America.
50 NM lateral separation is not applied on routes defined by ground navigation aids or on Gulf RNAV Routes Q100, Q102, or Q105.
Useful information for flight planning and operations over the Gulf of America, under this 50 NM lateral separation policy, as well as information on how to obtain RNP 10 or RNP 4 authorization, can be found in the West Atlantic, Gulf of America, and Caribbean Resource Guide for U.S. Operators located at: https://www.faa.gov/headquartersoffices/avs/wat-gomex-and-caribbean-resource-guidehttps://www.faa.gov/headquartersoffices/avs/wat-gulf-and-caribbean-resource-guide.
4-7-2 Accommodating Non-RNP 10 Aircraft
Operators not authorized for RNP 10 or RNP 4 may still file for any route and altitude within the Gulf of America CTAs. However, clearance on the operator's preferred route and/or altitude will be provided as traffic allows for 90 or 100 NM lateral separation between the non-RNP 10 aircraft and any others. Priority will be given to RNP 10 or RNP 4 aircraft.
Operators of aircraft not authorized RNP 10 or RNP 4 must include the annotation “RMK/NONRNP10” in Item 18 of their ATC flight plan.
Pilots of non-RNP 10 aircraft are to remind ATC of their RNP status; i.e., report “negative RNP 10” upon initial contact with ATC in each Gulf CTA/FIR.
Operators will likely benefit from the effort they invest to obtain RNP 10 or RNP 4 authorization, provided they are flying aircraft equipped to meet RNP 10 or RNP 4 standards.
4-7-3 Obtaining RNP 10 or RNP 4 Operational Authorization
For U.S. operators, AC 90-105, Approval Guidance for RNP Operations and Barometric Vertical Navigation in the U.S. National Airspace System and in Oceanic and Remote Continental Airspace, provides the aircraft and operator qualification criteria for RNP 10 or RNP 4 authorizations. FAA personnel at flight standards district offices (FSDO) and certificate management offices (CMO) will use the guidance contained in AC 90-105 to evaluate an operator's application for RNP 10 or RNP 4 authorization. Authorization to conduct RNP operations in oceanic airspace is provided to all U.S. operators through issuance of Operations Specification (OpSpec), Management Specification (MSpec), or Letter of Authorization (LOA) B036, as applicable to the nature of the operation; for example, part 121, part 91, etc. Operators may wish to review FAA Order 8900.1, Flight Standards Information Management System, volume 3, chapter 18, section 4, to understand the specific criteria for issuing OpSpec, MSpec, and/or LOA B036.
The operator's RNP 10 or RNP 4 authorization should include any equipment requirements and RNP 10 time limits (if operating solely inertial-based navigation systems), which must be observed when conducting RNP operations. RNP 4 requires tighter navigation and track maintenance accuracy than RNP 10.
4-7-4 Authority for Operations with a Single Long-Range Navigation System
Operators may be authorized to take advantage of 50 NM lateral separation in the Gulf of America CTAs when equipped with only a single long-range navigation system. RNP 10 with a single long-range navigation system is authorized via OpSpec, MSpec, or LOA B036, Table 2. Operators should contact their FSDO or CMO to obtain information on the specific requirements for obtaining B036. Volume 3, chapter 18, section 4 of FAA Order 8900.1 provides the qualification criteria to be used by FAA aviation safety inspectors in issuing B036.
4-7-5 Flight Plan Requirements
In order for an operator with RNP 10 or RNP 4 authorization to obtain 50 NM lateral separation in the Gulf of America CTAs/FIRs, and therefore obtain preferred routing available to RNP authorized aircraft, the international flight plan form (FAA 7233-4) must be annotated as follows:
Item 10a (Equipment) must include the letter “R.”
Item 18 must include either “PBN/A1” for RNP 10 authorization or “PBN/L1” for RNP 4 authorization.
Indication of RNP 4 authorization implies the aircraft and pilots are also authorized RNP 10.
Chapter 5, Section 1, of this manual includes information on all flight plan codes. RNP 10 has the same meaning and application as RNAV 10. They share the same code.
4-7-6 Contingency Procedures
Pilots operating under reduced lateral separation must be particularly familiar with, and prepared to rapidly implement, the standard contingency procedures specifically written for operations when outside ATC surveillance and direct VHF communications (for example, the oceanic environment). Specific procedures have been developed for weather deviations. Operators should ensure all flight crews operating in this type of environment have been provided the standard contingency procedures in a readily accessible format. The margin for error when operating at reduced separation mandates correct and expeditious application of the standard contingency procedures. These internationally accepted procedures are published in ICAO Document 4444, chapter 15. The procedures are also reprinted in the U.S. Aeronautical Information Publication (AIP), En Route (ENR) Section 7.3, Special Procedures for In-flight Contingencies in Oceanic Airspace; and AC 91-70.