What does PBN/ in Field 18 of an ICAO flight plan mean and when is it required?

PBN/ (Performance-Based Navigation) is a Field 18 indicator that lists the specific RNAV and RNP specifications the aircraft is approved to fly, using two-character codes such as A1 for RNAV 10, L1 for RNP 4, or S1 for RNP Approach. It is required any time the letter R appears in Field 10a of the ICAO flight plan. Omitting PBN/ when R is filed will cause the flight plan to be rejected by ATC automation systems. Dispatchers must ensure every code listed in PBN/ is supported by actual aircraft approval and crew qualification.

What is the difference between Field 10a and Field 10b on an ICAO flight plan?

Field 10 is split into two subfields: 10a covers communication, navigation, and approach aid equipment (such as S for standard, R for PBN approval, W for RVSM, G for GPS), while 10b covers surveillance equipment (such as C for Mode C, S for Mode S transponder, and E for 1090 MHz ADS-B Out). The two subfields are separated by a forward slash when written. A common source of confusion is that the letter S means 'standard avionics' in 10a but 'Mode S transponder' in 10b — the meaning depends entirely on which subfield it appears in.

What ICAO flight plan codes are required to fly North Atlantic tracks or Pacific oceanic routes?

For North Atlantic Organized Track System (NAT OTS) operations, aircraft typically need RVSM (W in Field 10a), RNAV 10 or RNP 4 PBN approval (A1 or L1 in the PBN/ indicator in Field 18), and CPDLC/ADS-C datalink capability indicated by J1 or J4 codes in Field 10a along with SUR/RSP180 in Field 18 for PBCS compliance. Pacific oceanic routes often require RNAV 10 (A1) as a minimum and may require RNP 4 (L1) for reduced lateral separation. Dispatchers must verify that OpSpecs authorize each capability before filing those codes.

Filing the ICAO Flight Plan: Equipment Codes and PBN Descriptors for Dispatchers

When an aircraft dispatcher files an international or domestic ICAO-format flight plan, the document that ATC controllers, route automation systems, and foreign aviation authorities receive is only as reliable as the equipment codes entered in the plan. Unlike the older FAA domestic flight plan format, the ICAO flight plan uses a structured series of capability fields that describe exactly what avionics are on board, what surveillance transponder modes the aircraft can support, and—critically for modern oceanic and RNAV operations—what Performance-Based Navigation (PBN) specifications the aircraft can meet. Errors in these fields are not merely clerical problems; they can trigger route rejections, strip the flight of preferred oceanic tracks, cause ATC to withhold altitude assignments, or expose the operator to regulatory scrutiny after the fact.

The authoritative domestic references for ICAO flight plan filing are the FAA Instrument Procedures Handbook (FAA-H-8083-16) and Chapter 5 of the Aeronautical Information Manual (AIM). Together they describe the ICAO flight plan form (ICAO Doc 4444 format as adopted in the U.S.), the meaning of each field, and the specific codes dispatchers must understand. This article provides a dispatcher-focused, in-depth treatment of Fields 10 and 18, the two fields that carry equipment and PBN information.

The ICAO Flight Plan at a Glance

The ICAO flight plan is divided into numbered fields. For dispatchers, the most operationally significant are Field 7 (aircraft identification), Field 8 (flight rules and type of flight), Field 9 (number/type/wake turbulence category), Field 10 (equipment and capabilities), Field 13 (departure aerodrome and time), Field 15 (route), Field 16 (destination and alternates), Field 18 (other information), and Field 19 (supplemental information). Fields 10 and 18 work as a pair: Field 10 gives ATC automation a concise coded summary, while Field 18 provides the detail that automation cannot convey in single-letter codes.

Field 10: Equipment and Capabilities

Field 10 is divided into two subfields separated by a forward slash: 10a (COM/NAV/approach aids) and 10b (surveillance equipment). Both use single-letter or letter-number codes defined in ICAO Doc 4444 and reproduced in the AIM.

Each letter represents a category of installed, serviceable, and crew-qualified equipment. A dispatcher must verify that the equipment listed is not only physically on the aircraft but also airworthy and approved for the intended operation. Common codes include:

S — Standard equipment (VHF radio, VOR, ILS). If the aircraft has only basic standard avionics, enter S.
R — PBN approved. This code is mandatory any time the aircraft is approved for any RNP or RNAV specification. When R is entered, Field 18 must contain a PBN/ indicator with specific descriptor codes (see below).
G — GPS/GNSS. Entered when GPS is installed and approved; if GPS is the basis for PBN approval, both G and R are typically entered together.
D — DME.
F — ADF.
O — VOR.
I — ILS.
C — LORAN-C (now rarely used).
X — MNPS approved (relevant for certain North Atlantic operations).
W — RVSM approved. This is one of the most operationally critical codes for dispatchers operating in domestic and international RVSM airspace (FL290–FL410). Without W, ATC cannot assign RVSM altitudes, severely limiting routing options on transcontinental and transatlantic operations.
Y — 8.33 kHz VHF radio spacing (required in much of European airspace).
E1/E2/E3 — FMC/ACARS/FANS-1/A+ datalink capabilities (CPDLC, ADS-C).
J1–J7 — Various CPDLC and datalink capabilities. J1 is CPDLC ATN VDL Mode 2; J2 is FANS 1/A HF data link; J4 is FANS 1/A VDL Mode 2 — extremely important for oceanic PBCS (Performance Based Communication and Surveillance) operations.

If no COM/NAV equipment beyond standard is carried, enter N in Field 10a. Never leave Field 10a blank.

Field 10b — Surveillance Equipment

The surveillance subfield describes transponder and ADS-B capability:

N — No surveillance equipment.
A — Mode A transponder (4096 codes).
C — Mode A and Mode C (altitude reporting).
S — Mode S transponder with aircraft identification and pressure altitude.
E — Mode S with aircraft identification, pressure altitude, and extended squitter (ADS-B). Note the letter E here refers to ADS-B Out with 1090 MHz extended squitter — not the same as the E1/E2/E3 datalink codes in 10a.
H — Mode S with enhanced surveillance (DAPs, used primarily in European airspace).
L — Mode S with aircraft ID, pressure altitude, extended squitter, and enhanced surveillance.
U — ADS-B Out with UAT (978 MHz) — applicable to some GA aircraft operating under 14 CFR Part 91.225.
V — ADS-B Out with VDL Mode 4 (rare in U.S. operations).
B1/B2 — ADS-B with dedicated in/out capability on specific frequencies (used in certain international contexts).

For most U.S. airline operations, the surveillance field will read something like /SEB2 or /SE, reflecting Mode S plus 1090 MHz ADS-B Out. Dispatchers should confirm the aircraft's actual transponder and ADS-B certification before filing, especially for wet-lease or charter operations involving unfamiliar equipment.

Field 18: Other Information and the PBN Descriptor

Field 18 is a free-text expansion field. When Field 10a contains the letter R (PBN approved), the dispatcher must include a PBN/ indicator in Field 18 followed by descriptor codes that tell ATC and route automation exactly which PBN specifications the aircraft can meet. This is not optional — omitting PBN/ when R is filed, or filing R without PBN/, will cause the flight plan to be rejected by modern ATC processing systems.

PBN Descriptor Codes in Field 18

The PBN codes are grouped by navigation specification type. The AIM and FAA-H-8083-16 list the approved codes; the most operationally important for dispatchers include:

A1 — RNAV 10 (RNP 10). Required for certain Pacific oceanic routes where lateral separation is based on 50 NM or 100 NM track spacing.
B1 — RNAV 5 (all sensors). Common in European airspace.
B2/B3/B4/B5/B6 — RNAV 5 with specific sensor subsets (VOR/DME, DME/DME, ILS/MLS, GNSS, etc.).
C1–C4 — RNAV 2 (various sensor combinations). C1 is RNAV 2 with any approved sensor; C2 is GNSS; C3 is DME/DME; C4 is DME/DME/IRU.
D1–D4 — RNAV 1 (similar sensor subsets). D1 with all sensors, D2 GNSS, D3 DME/DME, D4 DME/DME/IRU.
L1 — RNP 4. Required for some South Pacific and Pacific routes where lateral accuracy of ±4 NM (95%) is needed.
O1–O3 — Basic RNP 1 with various sensors.
S1/S2 — RNP APCH (APV Baro-VNAV) and RNP APCH with SBAS. Required to conduct RNAV (GPS) and RNP approaches.
T1/T2 — RNP AR APCH (curved path, RF legs) with and without RF capability. Required for authorization-required RNP approaches (formerly RNAV Special Aircraft and Aircrew Authorization Required).
P1/P2 — Reserved for certain RNP specifications used in approach contexts.

A typical long-haul airline filing might include PBN/A1B1C1D1L1O1S1, indicating the aircraft is approved for RNAV 10, RNAV 5, RNAV 2, RNAV 1, RNP 4, Basic RNP 1, and RNP Approach operations. Dispatchers must cross-reference the aircraft's approved operations specifications (OpSpec) and the aircraft flight manual supplement to ensure every code listed is actually authorized — filing a code the aircraft does not hold is a regulatory violation and a safety hazard.

Other Field 18 Indicators

Besides PBN/, dispatchers frequently use:

NAV/ — Significant navigation equipment not covered by Field 10 codes (e.g., NAV/RNVD1E2LVLASO for specific FANS capability descriptions).
COM/ — Communication equipment not described in Field 10a.
SUR/ — Surveillance capability details, including PBCS compliance (e.g., SUR/RSP180 ADSB for certain North Atlantic operations).
DAT/ — Data capability details.
RMK/ — Remarks meaningful to ATC.
SEL/ — SELCAL code, essential for HF-equipped oceanic operations.
RVR/ — Minimum RVR capability for low-visibility operations.

Why It Matters for Dispatchers

Dispatchers bear legal and operational responsibility for the accuracy of the flight plan under 14 CFR Part 121. An incorrect equipment code can result in ATC assigning an altitude that is below RVSM airspace (losing time and fuel efficiency), rejection of a preferred oceanic track, inability to conduct datalink communications required for Reduced Vertical Separation in certain foreign FIRs, or post-flight enforcement action. For Part 135 dispatchers, the same accuracy standards apply. Equally important: filing capability codes the aircraft does not actually hold—such as claiming RNP AR when the crew is not trained and the aircraft is not authorized—creates a false safety assurance that could contribute to an accident.

Key Numbers and Rules

RVSM airspace in the U.S.: FL290–FL410 inclusive. Aircraft must have W in Field 10a.
ADS-B Out required under 14 CFR §91.225 in Class A, B, C airspace, above 10,000 ft MSL, and within 30 NM of Class B airports. Code E (1090 ES) or U (UAT) in Field 10b.
When R is in Field 10a, PBN/ in Field 18 is mandatory — no exceptions.
RNP 10 (A1) is the minimum PBN spec for many Pacific oceanic routes; RNP 4 (L1) enables tighter lateral separation standards.
North Atlantic Organized Track System (NAT OTS) typically requires RNAV 10 or RNP 4, RVSM, and CPDLC/ADS-C (J codes and SUR/RSP180).
Maximum number of PBN codes in a single PBN/ indicator: up to 8 codes may be listed (some systems limit display length).

Common Test Traps

Omitting PBN/ when R is filed. The exam often presents a flight plan with R in Field 10a but no PBN/ in Field 18 and asks whether it is correct. It is not — the plan would be rejected.
Confusing Field 10b surveillance codes with Field 10a datalink codes. The letter E means ADS-B Out in 10b but has a completely different meaning in the datalink context (E1/E2/E3) in 10a. Read the subfield carefully.
Assuming S in Field 10a means standard when it appears in Field 10b. In 10b, S means Mode S transponder. Context matters — S in 10a = standard equipment; S in 10b = Mode S transponder.
Filing W without verifying OpSpec authorization. RVSM requires both airframe certification and operational authorization (OpSpec B046 for Part 121). The dispatcher must confirm both.
Listing PBN approach codes (S1, T1) based on avionics alone. RNP APCH and especially RNP AR APCH require explicit OpSpec authorization and trained crews — a GPS-equipped aircraft is not automatically RNP AR capable.