Questions over unexplained technical signals, possible electrical disturbances and engine shutdown mechanisms have resurfaced in the AI-171 crash investigation, with Federation of Indian Pilots (FIP) asking Aircraft Accident Investigation Bureau (AAIB) to closely examine ACARS (aircraft communications addressing and reporting system) maintenance messages, FADEC fail-safe systems and previously flagged discrepancies before technical causes are set aside.In a detailed letter sent to AAIB on Friday, FIP president Capt CS Randhawa referred to newly obtained technical material, including ACARS maintenance messages reportedly transmitted after take-off, publicly available documents relating to Full Authority Digital Engine Control (FADEC) systems, and previously highlighted concerns around RAT deployment chronology and said these issues required closer examination as part of the ongoing investigation.The pilots’ body said the submission places on record “ACARS maintenance messages transmitted before after the aircraft got airborne, a design feature in the FADEC that permits auto shutdown of both engines”, while linking these issues with earlier concerns regarding electrical disturbances, simulator validation requests and flight-data timelines.According to the letter also copied to the Civil Aviation Minister, PMO, Civil Aviation Secretary and DGCA, 10 ACARS maintenance messages were reportedly transmitted by AI-171 after becoming airborne at around 08:08:39 UTC on June 12, 2025. FIP requested that investigators examine the relevance of these maintenance messages to the accident sequence and determine whether they were evaluated during the investigation.The federation also referred to publicly available technical documents relating to FADEC fuel-metering fail-safe logic. Citing extracts reproduced in its submission, FIP noted that failures in specific control loops could switch fuel flow to a fail-safe minimum position that “may result in an in-flight shutdown (IFSD) of the engine”.Based on the maintenance messages and technical material cited, FIP proposed what it described as a second technical theory involving electrical disturbances affecting aircraft systems.“Electrical disturbance involving abnormal current flow, arcing, insulation breakdown, or grounding-path current could propagate into the Boeing 787 Common Core avionics/network environment,” the letter stated. According to the federation, such disturbances could temporarily disrupt or corrupt Common Core data channels supplying engine-interface information to both EEC systems, potentially resulting in simultaneous FADEC protective responses and consequent in-flight shutdown of both engines.The representation also revisited concerns previously flagged by FIP relating to discrepancies in RAT deployment chronology, DFDR time-reference reconciliation, simulator validation and electrical-system failure pathways.Referring to media reports and witness accounts concerning Captain Sumeet Sabharwal, the federation said multiple reports had claimed that the pilot’s body was recovered while still gripping the flight controls. FIP argued that such reported observations “would be consistent with continued recovery attempts during the final phase of flight” and questioned why these observations were not discussed in the preliminary report or autopsy findings.FIP asked AAIB to direct Air India to submit original ACARS maintenance messages before investigators and clarify why these messages were allegedly not highlighted earlier “to prevent premature attribution of pilot suicide theories which were leaked by ‘authorities’ to foreign media”.The federation also sought Boeing’s technical interpretation of the maintenance-message strings, saying operators may not possess independent decoding capability for such identifiers, and asked whether these messages had been evaluated before “excluding technical causes in the preliminary AAIB report and giving a clean chit to M/s Boeing”.The letter further sought specific responses in the final report to issues raised in previous submissions, including RAT deployment chronology, simulator validation, electrical-system failures and witness observations.Quoting ICAO guidance, FIP said accident investigations require all possible causes to be systematically evaluated and eliminated before conclusions are reached. It also urged AAIB not to issue an interim report, arguing that such a document could “lead to greater confusion and speculations” and may prove detrimental to the investigation.“Technical discrepancies associated with RAT deployment chronology should be clarified and probable causes due to electrical-system failure pathways and the ACARS maintenance messages transmitted before and after the aircraft became airborne should not be excluded,” the letter said.