Investigation brief · generated 2026-10-09 · source: NTSB public docket and accident database
BOEING 737 7H4 — Philadelphia, PA, USA, 2018-04-17
NTSB number
DCA18MA142
Operator
SOUTHWEST AIRLINES CO
Registration
N772SW
Highest injury
Fatal · 1 fatal
Regulation
Part 121
Damage
Substantial
Cohort
Major investigation
Recorder data
Tier 1 — decoded recorder tables
Every sentence below is taken directly from NTSB records — the accident database, the docket's recorder reports and the Board's findings — with its source noted. Nothing is paraphrased or inferred.
NTSB summary
The NTSB's full report is available at http://www.ntsb.gov/investigations/AccidentReports/Pages/AccidentReports.aspx. The Aircraft Accident Report number is NTSB/AAR-19/03.
On April 17, 2018, about 1103 eastern daylight time, Southwest Airlines flight 1380, a Boeing 737-7H4, N772SW, experienced a left engine failure while climbing through flight level 320 en route to the flight's assigned cruise altitude. The flight had departed from LaGuardia Airport, Queens, New York, about 30 minutes earlier. As a result of the engine failure, the flight crew conducted an emergency descent and diverted to Philadelphia International Airport (PHL), Philadelphia, Pennsylvania. Portions of the left engine inlet and fan cowl separated from the airplane, and fragments from the inlet and fan cowl struck the left wing, the left-side fuselage, and the left horizontal stabilizer. One fan cowl fragment impacted the left-side fuselage near a cabin window, and the window departed the airplane, which resulted in a rapid depressurization. The airplane landed safely at PHL about 17 minutes after the engine failure occurred. Of the 144 passengers and 5 crewmembers aboard the airplane, 1 passenger received fatal injuries, and 8 passengers received minor injuries. The airplane was substantially damaged. The regularly scheduled domestic passenger flight was operating under the provisions of Title 14 Code of Federal Regulations Part 121 with a destination of Dallas Love Field, Dallas, Texas.
The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
A low-cycle fatigue crack in the dovetail of fan blade No. 13, which resulted in the fan blade separating in flight and impacting the engine fan case at a location that was critical to the structural integrity and performance of the fan cowl structure. This impact led to the in-flight separation of fan cowl components, including the inboard fan cowl aft latch keeper, which struck the fuselage near a cabin window and caused the window to depart from the airplane, the cabin to rapidly depressurize, and the passenger fatality.
A low-cycle fatigue crack in the dovetail of fan blade No. 13, which resulted in the fan blade separating in flight and impacting the engine fan case at a location that was critical to the structural integrity and performance of the fan cowl structure. This impact led to the in-flight separation of fan cowl components, including the inboard fan cowl aft latch keeper, which struck the fuselage near a cabin window and caused the window to depart from the airplane, the cabin to rapidly depressurize, and the passenger fatality.
Verbatim, NTSB determination.
Flight data recorder
Boeing 737-700 · N772SW — 399,807 samples, 120 parameters, 10:30:18.4 to 11:23:09.4.
Parameter
Max
at
Min
at
Final
at
Pressure altitude ft
32,648.0
11:03:33.1
104.0
11:20:37.1
214.0
11:23:09.1
Computed airspeed kts
308.0
10:52:33.0
45.0
10:30:19.0
45.0
11:23:09.0
Vertical acceleration g
1.7
11:03:58.0
0.6
11:03:42.5
1.0
11:23:09.3
Engine 1 N1 %RPM
99.6
11:03:31.8
0.0
10:30:18.8
0.0
11:23:08.8
Engine 2 N1 %RPM
99.8
11:03:37.3
16.4
10:30:19.3
20.1
11:23:09.3
Computed from the docket's tabular attachment; times as recorded (local or SRN as published).
Sequence of events (FDR factual report)
Time
Event
Page
10:31 (approx)
Engines started, number two (right) engine first and number one (left) engine second
4
10:42:34
Engines began accelerating to takeoff power
4
10:43:11
Pitch began to increase at computed airspeed of 123 kts
4
10:43:20
Gear weight on wheels signal transitioned from ground to air at computed airspeed of 157 kts
4
~10:50
Aircraft climbed steadily for about seven minutes to a pressure altitude of about 17,250 ft
5
~10:57
After three minutes at 22,000 ft, aircraft began to climb again
5
11:03:33.2
Approximate time of fan blade off event; pressure altitude about 32,648 ft; engine 1 fan and core speeds decreased immediately and engine 1 vibration levels were elevated
5
11:03:33.3
Discontinuity occurred in the data with missing data of at least 0.09 seconds, likely due to a momentary power interruption to the recording system
5
11:03:35
Engine 1 control recorded a flameout protection recovery mode active
5
11 seconds after discontinuity (~11:03:44.3)
Aircraft reached peak recorded value of 41.3 degrees left roll before coming back to level attitude; roll was uncommanded, pilot inputs and force to the right
5
11:03:39
Cabin Altitude Warning recorded, signifying cabin altitude exceeded 10,000 ft
5
11:03:43
Aircraft began a rapid descent with descent rates in excess of 5,000 feet per minute
5
11:03:48
Engine 1 Fault Dispatch Level A fault was recorded, correlated to a T12 (fan bypass duct temperature) fault
5
11:04:09
Engine 1 fuel switch position transitioned from Run to Cutoff, ending flameout protection recovery mode
4
11:12:24
Cabin Altitude Warning ceased when aircraft pressure altitude was about 9,150 ft
5
11:20:30
Aircraft touched down with flaps set at 5 degrees at approximately 171 kts; reverse thrust used on right engine
5
Extracted by claude-sonnet-5; 12 of 16 stated events verified against the raw recorder data.
Cockpit voice recorder
672 transcribed utterances from 10:52:58 to 12:39:03, 32 sources. Final entries:
12:35:38
CAM-2
DOM is going to take it just leave it * leave * the APU goin'.
12:35:42
CAM-1
okay.
12:35:56
CAM
[unintelligible background conversations].
12:38:56
CAM
[sound similar to fire siren].
12:39:03
CAM
[sounds consistent with ground personnel entering the plane for movement off the field].
The NTSB cautions that a CVR transcript is not a precise science and should not be used as the sole source of information.