Flight DL-1780 | Registration: N535DN
Date: 21 March 2025 | Location: Boston Logan International Airport (BOS)
Introduction
On 21 March 2025, a Delta Airlines Airbus A321-200neo (A321NX), registration N535DN, operating flight DL-1780 from Boston Logan International Airport (KBOS) to San Juan Luis Muñoz Marín International Airport (TJSJ), Puerto Rico, experienced an in-flight smoke event shortly after takeoff. The aircraft, carrying 197 occupants, returned to Boston and landed safely approximately 13 minutes after departure. The crew reported smoke and an associated odour in the cabin, prompting a precautionary return.
Flight Summary
• Operator: Delta Air Lines
• Aircraft Type: Airbus A321-271NX (neo)
• Registration: N535DN
• Engines: 2 × Pratt & Whitney PW1133G-JM
• Flight Number: DL-1780
• Callsign: DAL1780
• Route: Boston Logan (BOS/KBOS) to San Juan (SJU/TJSJ)
• Occupants: 197 (passengers and crew)
• Departure Runway: 27
• Landing Runway: 33L
• Incident Altitude: ~3,000 feet
• Time to Landing After Departure: Approx. 13 minutes
• Nature of Incident: Smoke and odour in cabin
• Injuries: None reported
• Damage: None reported
• Weather Conditions: VMC, surface wind 280° at 10 knots, visibility 10 SM, few clouds at 25,000 ft
Sequence of Events
Takeoff and Initial Climb
At approximately 08:36 local time, the aircraft departed from Boston’s runway 27. During initial climb, as the aircraft reached an altitude of approximately 3,000 feet, the flight crew received reports of smoke and a strong odour in the cabin. The exact source of the smoke was not visually confirmed at the time, and there was no indication of fire from the aircraft’s fire detection systems.
Crew Response
The pilots immediately donned their oxygen masks and declared an emergency to ATC. The decision was made to discontinue the climb and initiate a return to Boston. The aircraft was vectored for an expedited approach to runway 33L, which was the most favourable active runway under the prevailing conditions.
During the descent and landing rollout, the flight crew reported that although the visible smoke had dissipated, a residual burning smell remained in the cabin.
Landing and Taxi
The aircraft landed safely at 08:49 local time. Emergency services were standing by but were not required to intervene directly. The aircraft taxied under its own power to the terminal gate. All passengers disembarked without injury or further incident.
Post-Flight Inspection & Aircraft Status
A post-flight inspection was carried out by Delta maintenance teams and supported by Boston Logan’s airport fire crews. Initial evaluations did not reveal any obvious signs of fire or electrical system failure, though investigations into possible causes focused on:
• Galley electrical components
• In-flight entertainment or power supply systems
• Environmental control systems (ECS) / air conditioning packs
The aircraft was removed from service and grounded for a full inspection and maintenance review. The investigation concluded without a formal incident report from the NTSB, as no mechanical failure or damage was ultimately discovered that met the threshold for federal inquiry.
The aircraft remained on the ground for approximately 60 hours and was returned to operational service on 23 March 2025.
Replacement Flight and Operational Impact
A replacement Airbus A321neo, registration N517DN, was dispatched to operate the disrupted service to San Juan. Flight DL-1780 eventually departed Boston and arrived in Puerto Rico with an overall delay of approximately 3 hours and 15 minutes.
Passengers were provided with compensation and refreshments during the delay. There were no reports of medical issues related to smoke inhalation among the passengers or crew.
Technical Considerations
Cabin Smoke & Odour Events
Smoke or odour in the cabin can be caused by a range of non-fire-related issues including:
• Oil contamination in bleed air systems
• Electrical overheating in in-flight entertainment (IFE) systems
• Short circuits or faults in galley ovens or coffee makers
• Overheating of recirculation fans or avionics cooling fans
Such events typically activate the aircraft’s smoke detection system if severe, although low-volume or localised events may escape sensor thresholds.
A321neo ECS Overview
The Airbus A321neo is equipped with two air conditioning packs and an advanced environmental control system. If contaminated bleed air enters the ECS due to oil seal leaks or other malfunctions, it can carry odours into the cabin.
Conclusion
Delta Airlines flight DL-1780, operated by an Airbus A321neo (N535DN), returned safely to Boston Logan International Airport shortly after departure on 21 March 2025 due to the presence of smoke and odour in the cabin. The incident was handled professionally by the flight crew, with no injuries or damage reported. Maintenance teams conducted inspections before returning the aircraft to service approximately 60 hours later. The root cause of the odour was not publicly disclosed.
Disclaimer
This report is based on publicly available information and operational data as of 26 March 2025. While every effort has been made to ensure accuracy, we cannot guarantee the completeness of the information provided. If you are the rightful owner of any referenced materials and wish them removed, please email takedown@cockpitking.com.
