Key Lime Air Flight 4216
Swearingen SW-4 and Frontier Airbus Industrie A-319 · Incident: near collision between aircraft while taxiing
Event
- NTSB case
- OPS07IA001
- 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
- Incident
- 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
- Unknown
- 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
- Instrument Meteorological Cond
Aircraft 1 · Swearingen SW-4
- Aircraft type
- Swearingen SW-4
- 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
- N425MA
- Operator
- Key Lime Air
- Onboard fatalities
- Unknown
- Route
- From Denver, COTo not recorded
- 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
- Unknown
- 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
- Taxi · to runway
- 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
- Near collision between aircraft
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- None
Aircraft 2 · Airbus Industrie A-319
- Aircraft type
- Airbus A-319
- 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
- N915FR
- Operator
- Frontier
- Onboard fatalities
- Unknown
- Route
- From St. Louis Lambert International Airport (STL), St. Louis, MOTo Denver International Airport (DEN), Denver, CO
- 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
- Landing · aborted
- 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
- Near collision between aircraft
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- None
Cause areas
- Pilot in command › Wrong taxi route, inadvertent
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
At 0728 MST (1428 UTC) a runway incursion occurred involving Key Lime Air (LYM) flight 4216, an SW4, and Frontier (FFT) flight 297, an A319, at Denver International Airport (DEN), Denver, Colorado.
At 0725:00, the DEN ground controller instructed LYM4216 to taxi to runway 34 via taxiways M and AA. According the SW4 pilot, blowing snow reduced his visibility and taxiway SC was covered with snow that prevented him from seeing the centerline lighting. As he attempted to find the centerline lighting, he saw blue taxi lights, followed them and turned onto runway 35L.
According to the recorded airport surface detection equipment (ASDE), LYM4216 entered runway 35L at taxiway M2 at 0727:06.
At 0728:10, the ground controller asked the LYM4216 pilot his location. The pilot advised he was abeam Signature. Once the controller asked his location, the pilot stated that he noticed that he was on a runway.
The First Officer of FFT297 reported, "the Captain and I were flying back to Denver from St. Louis. The weather had deteriorated in Denver so we prepared to fly a full instrument approach. We were cleared to land on runway 35L by tower. I believe we broke out of the clouds around 600 feet. The visibility conditions were ½ mile with blowing snow. We both looked down the runway and confirmed verbally to each other that the runway was clear. We didn't see the aircraft until we were about 100 to 50 feet or so above the deck. When it did come into sight, it was at least 2,000 feet down the runway. The winds combined with the prop wash from the aircraft along with blowing snow is what caused it to be obscured and out of sight. I immediately commenced a go around as soon as the aircraft was in sight. The tower was given warning from its collision avoidance system not more than a couple of seconds later."
At 0728:17, AMASS provided an aural and visual alert for an occupied runway and 4 seconds later, the tower controller instructed FFT297 to "go around". The aircraft missed colliding by approximately 50 feet.
Weather at the time of the incident was 600 overcast, 1100 broken, visibility 1/2 mile, light snow, mist, wind 030 at 12, runway visual range on runway 35L was 5,500 feet.
Probable cause
The probable cause of the incident was the Key Lime Air flight 4216 pilot's inadvertant entry onto the active runway. A contributing factor to the incident was the failure of the Denver tower ground and local controllers to detect the aircraft on the airport movement area safety system (ASDE) display and issue a go-around instruction to the arrival flight crew.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record OPS07IA001
- Event ID
- 20070110X00037
- Case number
- OPS07IA001
- 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, damage. 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: a0702a51a244d7502ec7553c73363dc56bf813d6325f5e8bee96993c0d9e0874; retrieved 2026-09-18T14:48:07.527Z.