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| Date: | Friday 10 May 2024 |
| Time: | 12:36 UTC |
| Type: |  Airbus A320-214 |
| Owner/operator: | IndiGo Airlines, opb SmartLynx Malta |
| Registration: | 9H-SLE |
| MSN: | 3475 |
| Year of manufacture: | 2008 |
| Engine model: | CFMI CFM56-5B4/P |
| Fatalities: | Fatalities: 0 / Occupants: 174 |
| Other fatalities: | 0 |
| Aircraft damage: | None |
| Category: | Incident |
| Location: | near Delhi -
 India
|
| Phase: | Approach |
| Nature: | Passenger - Scheduled |
| Departure airport: | Agartala-Singerbhil Airport (IXA/VEAT) |
| Delhi-Indira Gandhi International Airport (DEL/VIDP) | |
| Investigating agency: | DGAC India |
| Confidence Rating: |  Accident investigation report completed and information captured |
IndiGo Airlines flight 6E2306, an Airbus A320-214 (9H-SLE), and IndiGo Airlines flight 6E273J, an Airbus A320-251N (VT-IQY), were involved in an airprox incident near Delhi, India.
There was air traffic congestion in Delhi Terminal Airspace and several aircraft were holding. Indigo flights IGO273J and IGO2306 were following STAR JAL 6F for Runway 10, descending to FL160 and FL180, respectively. IGO273J was instructed to descend to FL150, which was correctly acknowledged by the flight crew. The Approach (APAA) controller later instructed IGO273J to descend to FL140 and IGO2306 to descend to FL160.The instruction was correctly read back by the crew of both aircraft. Subsequently, the APAA controller instructed IGO2306 to descend further to FL150 and instructed both aircraft to execute a right orbit to consume the
delay.
At 12:35 UTC, the APAA controller instructed IGO273J to descend to FL130. However, IGO273J did not read back the instruction. Instead, IGO2306 acknowledged the transmission intended for IGO273J and commenced the descent. At 12:35:32 UTC, a separation breach occurred between IGO2306 and IGO273J, and Automation System generated Current Conflict Alert. Additionally, a TCAS RA Alert was generated between the two aircraft at 12:36:23 UTC.
By 12:36:36 UTC, standard separation between IGO2306 and IGO273J was restored.
Probable Cause:
The investigation concluded that unauthorized descent initiated by IGO2306 resulted into breach of separation (twice) between IGO2306 and IGO273J. The failure of the APAA controller to notice the read back of the instruction by the unintended aircraft (IGO2306) was the contributory factor.
Accident investigation:
 |
|
Sources:
DGCA India
History of this aircraft
Other occurrences involving this aircraft
| 28 January 2014 | VP-CXW | Flynas | 0 | Kuwait Intl Airport (KWI/OKBK) |  |
non |
| 10 May 2023 | 9H-SLE | Air Peace, lsf Smartlynx Malta | 0 | Abuja-Nnamdi Azikiwe International Airport (ABV/DNAA) |  |
unk |
| Bird strike | ||||||
| 1 September 2023 | 9H-SLE | Smartlynx Airlines Malta | 0 | Tallinn |  |
min |
| Bird strike | ||||||
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 26-Aug-2025 18:33 | ASN | Added |
Corrections or additions? ... Edit this accident description
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