.jpg)
Published by epochtimes, a purported internal complaint letter attributed to China Southern Airlines' Engineering and Technology Branch has circulated online, alleging a series of technical defects affecting newly delivered COMAC C919 aircraft and reigniting scrutiny over the reliability of China's first domestically developed narrowbody airliner.
The document, reportedly dated 27 May 2026, has not been independently authenticated, and neither China Southern Airlines nor Commercial Aircraft Corporation of China (COMAC) has publicly confirmed its authenticity.
Nevertheless, the allegations have generated significant discussion within the aviation community because they concern aircraft that are already in active commercial service.
According to the circulating document, engineers identified multiple defects on two recently delivered C919 aircraft, including:
Oil leakage in the dry wing bay
Failure of fire detection loop supports
Flap panel detachment
Jammed wing anti-icing valves
Burnt electrical power panel in the rear galley
The letter reportedly claims that some of these issues had already been identified during production acceptance or flight-test activities but continued to appear after the aircraft entered airline service.
If accurate, the airline is said to have requested COMAC to fully disclose all previously identified technical issues and provide corrective action plans to restore customer confidence.
Although none of the reported defects automatically indicates an unsafe aircraft, each involves systems that are important for continued airworthiness:
Dry Wing Bay Oil Leak: The dry wing bay is a structural compartment designed to remain free of fuel. Depending on aircraft configuration, it may contain hydraulic lines, electrical wiring, control cables, and structural members. An oil or hydraulic fluid leak in this area can originate from hydraulic actuators, lubrication systems, or associated components. Maintenance engineers investigate such leaks to determine their source, assess any contamination risk, and ensure no degradation of surrounding systems.
Fire Detection Loop Support: Modern transport aircraft employ continuous fire detection loops in areas such as engine nacelles, auxiliary power units, and cargo compartments. Support brackets keep these sensing loops correctly positioned. Damage or detachment of the supports could potentially affect sensor positioning or inspection requirements, although fire detection systems typically include redundancy and built-in fault monitoring.
Flap Panel Detachment: Flaps increase wing lift during take-off and landing, while panels surrounding flap mechanisms improve aerodynamic smoothness and protect internal mechanical components. A detached flap fairing or access panel does not necessarily compromise flight safety but requires immediate inspection because loose components could create aerodynamic drag or become foreign object debris (FOD).
Anti-Icing Valve Malfunction: Wing anti-icing systems protect leading-edge surfaces against ice accumulation during flight in icing conditions. Jammed valves may reduce or prevent hot bleed air from reaching protected surfaces. Aircraft dispatch procedures normally require such defects to be assessed under the Minimum Equipment List (MEL), with repairs completed before operating into conditions where anti-ice capability is required.
Burnt Galley Power Panel: Electrical distribution panels in aircraft galleys supply power to ovens, coffee makers, and catering equipment. A burnt power panel generally results in the loss of galley services rather than a direct flight safety issue. Commercial aircraft electrical systems include circuit protection, fault isolation, and fire protection features designed to prevent electrical faults from propagating to essential aircraft systems.
Industry experts note that newly introduced aircraft types frequently experience what manufacturers refer to as entry-into-service (EIS) issues. These are typically reliability-related problems discovered during the first years of commercial operations as airlines accumulate operational experience under varying environmental and operational conditions.
Such issues are far from unique to the C919:
Both the Boeing 787 Dreamliner and Airbus A350 experienced numerous service bulletins, software updates, and component modifications during their early operational years as manufacturers refined aircraft systems based on airline feedback. The ultimate objective during this stage is to progressively improve dispatch reliability while maintaining certified safety standards.
The COMAC C919 entered commercial passenger service in 2023, representing a critical milestone for China's ambition to establish an indigenous commercial aircraft manufacturing industry capable of competing with Airbus and Boeing.
China Southern Airlines is among the programme's largest customers, having ordered 100 C919 aircraft, with deliveries scheduled through 2031. By July 2026, the airline had introduced 12 aircraft into commercial service.
Other Operators: Primary Chinese operators include China Eastern Airlines and Air China, while several overseas customers have announced plans to acquire or evaluate the aircraft.
Global Supply Network: The C919 is powered by CFM International LEAP-1C engines and incorporates numerous internationally supplied systems, including avionics, flight controls, and landing gear components sourced through global aerospace suppliers.
The aircraft programme has also encountered geopolitical challenges. In 2025, reports indicated that the United States tightened certain export licensing measures affecting technology supplied to COMAC, including components associated with Western aerospace manufacturers. Any long-term restrictions on international suppliers could present challenges for production planning, certification support, and spare parts availability, although COMAC continues pursuing increased domestic manufacturing capability.
At present, there is no indication from aviation regulators that the C919 fleet has been grounded or subjected to emergency airworthiness directives related to the issues described in the circulating document. It is critical to distinguish between reliability concerns and airworthiness:
| Category | Primary Focus | Regulatory / Operational Impact |
| Reliability Issues | Maintenance frequency, component durability, operational disruptions | Handled via routine maintenance, MEL, and manufacturer service bulletins |
| Airworthiness Concerns | Direct risk to the aircraft's ability to operate safely | Results in mandatory Emergency Airworthiness Directives (EADs) or fleet groundings |
Should the reported complaint prove authentic, it would primarily illustrate the operational challenges commonly encountered during the maturation of a new commercial aircraft programme. Whether the reported defects represent isolated production-quality issues or broader fleet-wide trends will depend on continued operational experience, manufacturer corrective actions, and oversight by aviation regulators.
.jpg)
