September 30, 2021


Review by Sofema Aviation Services (SAS) looking at the transition from ETOPS to EDTO


Any operation by an aeroplane with two or more turbine engines where the diversion time to an en-route alternate aerodrome is greater than the threshold time established by the State of the Operator.

Extended Diversion Time Operations (EDTO) Development-Background:

  • Initial State Letter circulated in 2007 (ref SP 59/4-07/47)
  • Special Operations Task Force (SOTF) set up in 2008
  • Second State Letter, with revised EDTO provisions circulated in June 2011
  • 7 Mar 2012: Amendment 36 to Annex 6 was adopted by Council
  • 16 July 2012: Effective date
  • 15 Nov 2012: Applicable date

Description of Extended Diversion Time Operations (EDTO)

  • EDTO is an evolution of ETOPS

o Based on existing ETOPS provision

o Applies to all commercial aeroplanes

o Addresses systems that could force an aeroplane to divert:

o Engines (for twins)

o Loss of pressurization

o Time-limited systems

Note – Requirements for 2 engines aeroplanes remains mostly unchanged.

Extended Diversion Time Operations (EDTO) General Criteria:

  • Requirements for 3 or more engines aeroplanes are based on good ā€œ industry practicesā€
  • No additional maintenance requirements nor additional certification requirements
  • Consideration of Time Limited System / identification of en-route alternates and verification of weather
  • Guidance on EDTO also provided in Annex 6 Attachment D

Extended Diversion Time Operations (EDTO) Crew Notes

Operators conducting operations beyond 60 mins to an en-route alternate aerodrome will require:

  • All en-route alternate aerodromes be identified.
  • The most up-to-date information be provided to the flight crew on identified en-route alternate aerodromes, including operational status and meteorological conditions.
  • Conditions at identified en-route alternate aerodromes in (2) above to be at or above the operatorā€™s established aerodrome operating minima for the operation at the estimated time of use (for 2 engines aeroplanes).
  • Also taking into account the operatorā€™s:

o Operational control and flight dispatch procedures

o Operational procedures

o Training programmes

Note – The EDTO threshold is not an operating limit. It is a flight time to an en-route alternate aerodrome, which is established by the State of the Operator.

When establishing an EDTO threshold the State needs to consider that:

  • The airworthiness certification of the aeroplane type does not restrict operations beyond the threshold time;
  • Specific flight dispatch requirements are met;
  • Necessary in-flight operational procedures are established; and
  • The operatorā€™s previous experience with similar aircraft types and routes is satisfactory.

EDTO Approval Requirements:

  • An EDTO approval is required for operations beyond the established EDTO threshold.
  • An EDTO approval should take into consideration:

o The aeroplaneā€™s EDTO significant systems (limiting time limitation, if any, and relevant to that particular operation).

o The operatorā€™s operational and EDTO experience with the aeroplane type.

Note – The operatorā€™s approved maximum diversion time should not exceed the most limiting EDTO significant system time limitation identified in the aeroplane flight manual.

EDTO Significant Systems

An aeroplane system whose failure or degradation could adversely affect the safety particularly of an EDTO flight, or whose continued functioning is specifically important to the safe flight and landing of an aeroplane during an EDTO diversion.


  • Propulsion systems
  • Hydraulic systems
  • Flight control systems
  • Electrical power
  • Equipment cooling systems
  • Pressurization systems
  • APU
  • Cargo compartment fire suppression systems
  • Fuel systems

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Annex 6 Attachment D, aviation, EDTO, ETOPS, Extended Diversion Time Operations, ICAO, Regulatory Compliance, SAS blogs, Special Operations Task Force (SOTF)