Communications:ACARS Traffic Log for MH370 (9M-MRO)/Background

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ACARS Traffic Log for MH370 (9M-MRO) - Background Details

All ACARS messages between Malaysia Airlines ground staff and their aircraft, including 9M-MRO, are processed by their service provider SITA. ACARS messages can be sent via (aeronautical) VHF datalinks if the aircraft is within range of a suitable VHF station on the ground. These are generally located at or near airports. Otherwise, ACARS messages can be sent and received using the satellite communications system. Malaysia Airlines contracted with Inmarsat to provide an aeronautical voice and data service. So the majority of messages to and from 9M-MRO were processed by SITA and simply relayed by Inmarsat. Each Log is marked © SITA because SITA is the Service Provider.


The data in the ACARS Traffic Log for MH370 was released in three stages:-

  1. March 2015

    The Malaysian ICAO Annex 13 Safety Investigation Team for MH370 released an Interim Statement on 8 March 2015 and information gathered by the Investigation Team was published in the Factual Information: Safety Investigation for MH370 MH370/01/15. Further details for some Sections of the Factual Information were provided in Appendices, numbered to match the relevant section.

    Section 1.9.4 Aircraft Communications Addressing and Reporting System (ACARS) describes ACARS generally and explains specific ACARS communications from MH370. The content of ACARS communications to and from MH370 (aircraft 9M-MRO) was provided in Appendix 1.9A - Acars Traffic Log. The 13-page Appendix only has scanned images of the ACARS messages. These have been manually transcribed here, but some characters were unreadable.

  2. July 2018

    On Monday, 30 July 2018 the Investigation Team publicly released the Safety Investigation Report MH370/01/2018.

    Section 1.9.4 Aircraft Communications Addressing and Reporting System is the same as, or similar to, the previous (2015) version, but the associated Appendix 1.9A - ACARS Traffic Log increased to 14 pages.

    The July 2018 version included three (pre-flight) ACARS messages using a VHF datalink before ACARS on the aircraft 9M-MRO was switched over to the SATCOM system. The Appendix content is text-based so the quality is clearer and more readable than previous.

  3. September 2018

    The revised Appendix 1.9A confirmed the existence of ACARS messages sent over VHF datalinks and raised the question - what else had not been released? Also, a set of messages from Malaysia Airlines ODC starting at 18:03:23 UTC had been cropped, rather than properly redacted: the sender requested MH370 to acknowledge the message and apparently signed his name, but instead of being properly redacted the signature line was crudely cut off. What else had been cut from the record or not made public?

    On 31 August 2018, Victor Iannello of The Independent Group posted MH370 Message Logs Were Edited – Updated and expressed disappointment that "more than four years after MH370’s disappearance, we [The Independent Group] are still asking Malaysia to release withheld data."

    On 7 September 2018 Malaysia responded by releasing a file named ACARS Traffic Log for MH370 (9M-MRO) which has 179 pages! Victor Ianello posted an update Malaysia Responds by Releasing Full Message Log and included a link to the source on the Ministry of Transport (Malaysia) website:-

    Note that the document ACARS Traffic Log for MH370 (9M-MRO) is not listed on the MoT public website for MH370:

    Key Items
    A summary of the additional content follows:-

    • The bulk of the additional content is Flight Planning System Interface Messages which were sent to the aircraft pre-flight (routinely) and significantly from 23:00:42 UTC - after contact with MH370 had been lost.

      The second set of instructions for the Flight Management System were actually a copy of data for a flight MH371 which is the normal return flight from Beijing to Kuala Lumpur. The intent was obviously to give instructions to the missing flight MH370 so it could 'find it's way home'. Sadly, these ground-to-air communications were not acknowledged by the SATCOM system on 9M-MRO.

    • Another previously unknown set of messages from Malaysia Airlines was sent at 18:38:51 UTC, and repeated. The content includes the line "DEAR MH370. PLS ACK TEST MSG. RGDS/OC.". There was no acknowledgement from MH370.

    Malaysia Airlines was criticised for apparently doing little to contact their own aircraft so it is good to finally see these attempts.

    Also, the Media Releases from Malaysia Airlines on Saturday, 8 March 2014 refer to a loss of contact at 2.40am MYT. As MYT is UTC plus 8 hours, this equates to 18:40 UTC - when the 'Dear MH370' messages were sent but not acknowledged. This provides a plausible explanation for the references to 2:40 am MYT.