Continental Airlines Flight 1521
Boeing 727-224 · Accident: partial loss of engine power (mechanical failure) during takeoff
From Miami International Airport (MIA) to George Bush Intercontinental Airport (IAH)
Event
- NTSB case
- MIA99FA005
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- 0
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- Airline
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Boeing 727-224
- Aircraft type
- Boeing 727
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N66734
- Operator
- Continental Airlines
- Onboard fatalities
- Unknown
- Route
- From Miami International Airport (MIA)To George Bush Intercontinental Airport (IAH), Houston, TX
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 121: Air Carrier
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Takeoff · roll/run
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Partial loss of engine power (mechanical failure)
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Other institution › Inadequate surveillance of operation
- Other maintenance personnel › Improper use of procedure
- Other maintenance personnel › Maintenance, overhaul, major, improper
Approximate · Estimated position: the centre of Miami, FL, the place the record names. Not the accident site.
NTSB narrative
During the initial part of the takeoff, prior to the engines reaching takeoff power, the No. 2 engine had an uncontained failure of the 8th stage HPC disk. The takeoff was aborted, the passengers were bussed to the terminal, and the aircraft was towed to the gate. Metallurgical examination of the 8th stage HPC disk showed that a significant amount of cadmium was present on steel base metal in the area of the fracture surfaces and the surface had an inadequate nickel coating. The disk had accumulated 359 flight hours since overhaul. The disk had been nickel-cadmium plated in March 1996 and was stored until February 1998, when it was installed in the accident engine during repair. Other HPC disk installed in the accident engine, which had been nickel-cadmium plated by the same company as the 8th stage HPC disk, were also found to have inadequate nickel coating. During nickel-cadmium plating the nickel acts as a barrier coating between the cadmium and the steel part to prevent cadmium from contacting the steel part, which can cause cadmium embrittlement.
Probable cause
The catastrophic failure of the 8th stage high pressure compressor disk from cadmium embrittlement as a result of improper adherence to the prescribed plating procedures and requirements by the company that last plated the disk. Contributing to the accident was the failure of the engine repair company to provide adequate surveillance and oversight of the plating company, the engine repair companies use of an unauthorized repair vendor, the plating company, and the engine repair companies failure to inform the aircraft operator that they had used the plating company which was not on the aircraft operators vendor list. Also contributing to the accident was the aircraft operators failure to audit the engine repair company to the level of detail that they would have discovered the engine repair company was using an unauthorized repair vendor.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record MIA99FA005
- Event ID
- 20001211X11298
- Case number
- MIA99FA005
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: ab6ca9ff9d4606a9b762e3bdc6f8c36543f9d5be336bfefa21fceebfb14babf8; retrieved 2026-09-18T17:04:08.300Z.