Southwest 737 diverted after metal debris found in right engine at 13,000 feet

Quick summary

Southwest Airlines flight WN-375 diverted back to Austin–Bergstrom International Airport on June 4, 2026, after pilots reported right-engine problems climbing through 13,000 feet en route to Phoenix. Post-landing inspection by airport fire services and a subsequent FAA examination found metal debris and physical damage inside the right engine of the 21-year-old Boeing 737. The aircraft has not returned to service. The FAA has opened an investigation.

No engine fire warning activated in the cockpit, leaving the exact failure mechanism unconfirmed. The incident lands against a backdrop of unresolved regulatory action on 737NG engine nacelles dating to the fatal 2018 Southwest engine failure.

Pilots on Southwest Airlines flight WN-375 declared an abnormal situation roughly 12 minutes after departing Austin on the morning of June 4, requesting an immediate return after the right engine on their 21-year-old Boeing 737 began showing anomalous indications. The aircraft climbed no higher than 13,000 feet before crews turned back.

Weather near Austin forced a brief holding pattern — the jet circled north of the city at around 5,000 feet before being cleared to land. It touched down safely approximately 40 minutes after departure. Airport fire crews held the aircraft on the runway for inspection before allowing it to taxi to the terminal under its own power.

What they found matters. The FAA’s examination of the right engine revealed metal debris and internal damage — physical evidence that something broke inside that engine at altitude. The aircraft has been grounded since. Investigators have not yet identified the source of the debris or confirmed whether any component separated during flight.

Pilots told air traffic control they had not received an engine fire warning. That detail is notable: it means standard cockpit alerting did not trigger the diversion. The crew acted on other indications — exactly the kind of judgment call that keeps incidents from becoming accidents.

What the FAA found — and what it still doesn’t know

Metal debris inside a running jet engine is not a maintenance footnote. It means something failed, shed material, or ingested a foreign object with enough force to leave physical evidence. The FAA’s confirmation of “metal debris and damage to the right engine” establishes this as a reportable incident requiring a formal investigation, not a precautionary return.

The aircraft involved is a 21-year-old Boeing 737NG — the same platform and engine family at the center of multiple prior regulatory actions. Its CFM56-7B engines are the same type that failed catastrophically on Southwest Flight 1380 in April 2018, when a fan blade separated from a low-cycle fatigue fracture, sent debris through the fuselage, and killed one passenger. That accident drove emergency FAA inspection orders within days and a subsequent multi-year nacelle modification program that, as of this writing, does not require full completion until 2028.

A separate incident adds context. In April 2024, a Southwest Airlines Boeing 737-800 departing Denver lost an engine cover — the inlet cowl — on takeoff. The cowling struck the wing flap before the aircraft returned safely. The FAA opened an investigation and the airline removed that aircraft from service. Two incidents involving engine or nacelle hardware on Southwest 737s within roughly two years is the kind of pattern regulators track.

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The nacelle modification program referenced above — covering 1,979 U.S.-registered 737NGs and thousands more worldwide — requires replacement or inspection of specific inlet cowl fasteners and crushable spacers on both engines. The 2028 deadline means a portion of the in-service fleet, including older aircraft like the one involved in Thursday’s diversion, may not yet have completed all mandated work. Whether this specific aircraft’s modification status is relevant to the June 4 incident is something investigators will establish. For now, the FAA has confirmed damage. The cause remains open.

Travelers on the AUS–PHX corridor can check Southwest’s flight status tool for real-time updates on this pairing while the investigation proceeds.

Why this incident fits a pattern regulators are already watching

The 2018 Flight 1380 accident was not just a tragedy — it was a regulatory inflection point. The FAA’s emergency response established that CFM56-7B fan blades in high-cycle service carried a fatigue risk that existing inspection intervals had not caught. The resulting ADs were designed to close that gap. But the nacelle modification program, which addresses what happens when a blade does separate, is still rolling out eight years later.

That timeline matters here. When investigators examine Thursday’s metal debris, one of the first questions will be whether the damage pattern resembles anything in the post-2018 incident record — and whether the aircraft’s modification and inspection history is current. The FAA routinely cross-references new incidents against existing AD compliance data. If a link emerges, a new or revised directive can follow within weeks. If the debris traces to an unrelated cause — a foreign object, a fastener, a component unconnected to prior ADs — the investigation scope narrows considerably.

It’s also worth noting that Southwest has faced broader scrutiny on maintenance and operational reliability in recent years. The Nashville near-miss in April 2026 — where two Southwest 737s came within 500 feet of each other after an ATC error — added to a string of incidents drawing FAA attention to the carrier’s operations. None of that predetermines the outcome here, but it shapes the regulatory environment in which this investigation will proceed.

For travelers, the practical reality is this: engine anomalies on individual aircraft cause isolated disruptions, not network collapse. The AUS–PHX route operates multiple daily frequencies on Southwest alone, and American Airlines runs nonstop service on the same pairing. One grounded aircraft creates a manageable gap — not a crisis, unless you happen to be booked on the specific rotation affected.

Steps to protect your Austin–Phoenix trip this week

Southwest is operating with one fewer aircraft on AUS–PHX rotations while this 737 remains grounded — equipment swaps and minor timing shifts are possible on this route through at least the next several days.

• Check flight status the morning of departure. Use your reservation number at southwest.com under “Flight Status,” then check again two hours before departure. An equipment change or extended delay on this pairing is the most likely disruption scenario.
• Call Southwest directly if your flight shows a significant delay. Southwest Reservations at 1-800-435-9792 can rebook you on an earlier or later same-day departure at no additional fare, subject to availability. Do this by phone — the app’s rebooking options are more limited during irregular operations.
• Know your backup before you need it. American Airlines operates nonstop AUS–PHX service. Pull up same-day fares on Google Flights now so you have a number in mind. If Southwest cannot accommodate you and your trip is time-sensitive, you can request a refund and rebook independently without scrambling for information at the gate.
• For critical connections beyond Phoenix, look at Southwest’s multi-city options via Dallas Love Field, Denver, or Las Vegas as same-day alternatives if the direct flight is compromised. Connections through those hubs add time but preserve your itinerary.

Watch: The FAA’s incident database and NTSB preliminary reports in the next 72 hours will indicate whether this investigation is being treated as routine or elevated — a meaningful signal for anyone monitoring Southwest’s 737NG fleet reliability.

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