Oceanic Contingency Procedures: The Complete ICAO Guide for Pilots

Introduction

An oceanic diversion can involve a long flight to a suitable alternate and a route across other traffic streams. Before explaining a turn or level change, establish why the aircraft needs to leave its clearance and whether a revised clearance can be obtained in time.

ICAO Doc 4444 (PANS-ATM), Section 15.2, covers in-flight contingencies in oceanic airspace. The references below use the public procedures in ICAO NAT Doc 007, Chapter 10 for the North Atlantic. Confirm the applicable regional procedures for other airspace.

This is an interview study guide. For flight operations, use current controlled references, aircraft procedures and regional instructions. North Atlantic communications and surveillance include CPDLC and ADS-B; availability depends on the area and aircraft equipment. An oceanic scenario should not assume that ATC contact or surveillance is absent everywhere.

1. The Three Main Contingency Scenarios

NAT Doc 007, paragraph 10.1.1, identifies cases these procedures are designed to address:

• Inability to comply with ATC clearance due to weather (meteorological conditions)
• En-route diversion across the prevailing traffic flow — e.g., a medical emergency requiring an immediate track change
• Loss or significant degradation of navigation capability — or a pressurization failure

Note: Degraded navigation procedures are also covered in ICAO Doc 4444, Chapter 5, section 5.2.2.

The pilot's judgement determines the sequence of actions for the circumstances. Obtain a revised clearance whenever possible, while taking the action necessary to keep the aircraft safe.

2. General contingency procedures

Step 1: Try to Get a Clearance First

If the aircraft cannot continue in accordance with its ATC clearance, obtain a revised clearance before taking action whenever possible. If the situation requires action before clearance can be obtained, use the applicable contingency procedure and advise ATC as soon as practicable.

Step 2: If No Clearance Can Be Obtained

The general procedure uses an offset track and flight level to reduce the likelihood of encountering other aircraft.

NAT Doc 007, paragraph 10.2.1:

a) Lateral offset — 5.0 NM

Turn at least 30 degrees left or right to establish a parallel, same-direction track offset by 5.0 NM (9.3 km).

The direction of turn should consider:

1. Aircraft position relative to any organized track or ATS route system
2. Direction of flights and flight levels on adjacent tracks
3. Direction to alternate airport
4. Any strategic lateral offset (SLOP) being flown
5. Terrain clearance

b) Traffic watch — ACAS

Maintain a visual and ACAS watch. Keep ACAS in RA mode at all times (unless aircraft limitations dictate otherwise).

c) Exterior lights

Turn on all exterior lights (within operating limitations).

d) Transponder

Keep the SSR transponder on and, when able, squawk 7700 as appropriate.

e) Notify ATC as soon as practicable

Advise ATC of any deviation from assigned clearance.

f) Communication means

Use voice and/or CPDLC as appropriate.

g) Voice distress/urgency signals

If voice is used:

• MAYDAY (distress) or PAN PAN (urgency) — preferably spoken three times

h) CPDLC emergency

If communicated via CPDLC, the controller may respond via CPDLC and may also attempt voice contact.

i) Broadcast on guard / inter-pilot frequency

Broadcast on 121.5 MHz (or backup: 123.45 MHz) at suitable intervals:

• Aircraft identification
• Nature of distress condition
• Pilot's intention
• Position (ATS route designator or track code)
• Flight level

3. Actions once offset from track

Once established on the 5.0 NM parallel, same-direction offset, the pilot faces a key decision.

NAT Doc 007, section 10.3, identifies factors including whether you're in a parallel track system, the potential for UPRs (User Preferred Routes) parallel to your route, the nature of the contingency, and weather at lower flight levels (e.g., convective activity).

Maintain the assigned flight level if possible

If possible, maintain the assigned flight level until established on the offset. If unable, initially minimise the rate of descent to the extent operationally feasible.

Once on the 5 NM offset: two options

Option A: Descend below FL 290 (NAT Doc 007, 10.3.2 a)

Descend below FL 290 and establish a 150 m (500 ft) vertical offset from normally-used flight levels. Proceed as required by the operational situation or per ATC clearance if obtained.

Note 1: "Normally used flight levels" are those in Annex 2 — Rules of the Air, Appendix 3.

Note 2: Descent below FL 290 is considered particularly applicable when there is a predominant traffic flow (e.g., east-west) or a parallel track system where your diversion path will likely cross adjacent tracks. It reduces the risk of conflict, ACAS RA events, and clearance delays.

Option B: Establish a vertical offset at the required level (NAT Doc 007, 10.3.2 b)

Establish and maintain a 150 m (500 ft) vertical offset from normally-used flight levels (or 300 m / 1000 ft if above FL 410). Proceed as required.

Note: Altimetry system error can reduce actual vertical separation. ACAS RAs may still occur with the 500 ft vertical offset.

4. Weather deviation procedures

Use the weather deviation procedure for avoidance of adverse meteorological conditions. Its altitude offsets differ from the general contingency procedure.

Request the weather deviation

When a weather deviation is required, initiate communications with ATC via voice or CPDLC. To get a rapid response:

• State "WEATHER DEVIATION REQUIRED" to indicate that priority is requested on the frequency, or
• Send a CPDLC lateral deviation request

If necessary, use the urgency call "PAN PAN" (preferably three times) or a CPDLC urgency downlink.

Important: The pilot shall inform ATC when the weather deviation is no longer required, or when the aircraft has returned to its cleared route.

When communications with ATC are established

The pilot requests clearance, advising the extent of deviation needed.

ATC will either:

• Issue clearance (if separation can be applied), or
• Advise the pilot of conflicting traffic and inability to clear, and request the pilot's intentions

The pilot then either:

• Complies with the ATC clearance, or
• Advises ATC of intentions and follows NAT Doc 007, 10.4.6

If a revised ATC clearance cannot be obtained

This section invokes the pilot-in-command authority (Annex 2, 2.3.1). If deviation is required to avoid weather and no clearance is available, an ATC clearance shall be obtained at the earliest possible time. Until then:

a) Deviate away from organized track/ATS route system if possible

b) Broadcast on 121.5 MHz (or 123.45 MHz backup)

At suitable intervals: aircraft ID, flight level, position (ATS route or track code), and intentions.

c) Watch for conflicting traffic — visual and ACAS

d) Turn on all exterior lights

e) Deviations < 5.0 NM from cleared track

Remain at the ATC-assigned level.

f) Deviations ≥ 5.0 NM from cleared track

When approximately 9.3 km (5.0 NM) from track, initiate a level change per the weather-deviation table below:

For example, on an originally cleared track of 090° magnetic, a right deviation of 5 NM or more calls for a 300 ft climb under this procedure. A left deviation calls for a 300 ft descent. Read both the original track direction and the side of deviation from the table; a geographical north/south shortcut can be misleading.

g) If a further deviation cannot be cleared

If ATC has cleared a deviation for a specified distance and you subsequently request but cannot obtain clearance to extend it, apply the 300 ft offset from normal cruising levels in accordance with the table before deviating beyond the cleared distance, as specified in NAT Doc 007, 10.4.6 g).

h) Returning to track

Be at your assigned flight level when within approximately 5.0 NM of the route centreline on the return, as specified in NAT Doc 007, 10.4.6 h).

i) Continue attempting to contact ATC throughout.

5. Quick Reference — Key Numbers to Remember

6. Worked interview example: weather ahead, clearance unavailable

Fictional prompt: You are PF on an originally cleared track of 090° magnetic. Avoiding a storm requires a right deviation beyond 5 NM, and you cannot obtain a revised clearance in time. Explain your actions using the NAT weather-deviation procedure.

I'd request the deviation early and tell ATC how far right we need to go. If waiting would take us into the weather, I'd fly the avoidance manoeuvre and ask the PM to broadcast our position and intentions, watch for traffic and keep trying ATC.

This is a weather deviation. With an originally cleared track of 090° and a right deviation beyond 5 NM, the table calls for a 300 ft climb when we're approximately 5 NM from the cleared track. I'd have the PM cross-check the direction and altitude change with me.

I'd keep ATC informed and obtain a revised clearance as soon as possible. On the return, we'd be back at the assigned level by approximately 5 NM from the route centreline.

The response identifies the weather threat, gives the communication tasks to the PM and selects the level change from the supplied track and deviation. It is a worked explanation of those facts, rather than a complete airborne checklist. Different facts, a clearance or an aircraft emergency can change the action required.

Practise changing the scenario

Repeat the question with a left deviation, then with a westbound track. Read the table each time. Next, replace the weather threat with a medical diversion across the traffic flow and explain why you would use the general contingency procedure.

For an actual emergency, the nature of the event determines what the crew can do first. Explain any need for immediate action before discussing an offset or waiting for a clearance.

References and scope

The contingency and weather-deviation provisions were checked on 26 October 2026 against ICAO NAT Doc 007, V.2026-1, Chapter 10 and the FAA AIP, ENR 7.3. NAT Doc 007 describes the North Atlantic environment; confirm the applicable regional requirements, current notices and controlled operator references for the flight concerned.