Incident Overview
On April 15, 2025, at about 2140 Atlantic daylight time, Frontier Airlines flight 3506, an Airbus A321-271NX (registration N607FR), experienced a hard landing on runway 10 at Luis Munoz Marin International Airport (SJU) in San Juan, Puerto Rico. The aircraft sustained damage to the nose landing gear and the number one engine. The flight, a scheduled domestic passenger service from Orlando International Airport (MCO) to SJU, carried 235 passengers and crew, none of whom were injured.
Flight Crew Actions
The first officer (FO) was the pilot flying, and the captain was the pilot monitoring during the night approach. The approach was stable but required a slight lateral correction to maintain centerline while descending through about 150 to 100 feet above ground level (agl). At 20 ft radio altitude, the aural RETARD alert sounded, and the FO recalled bringing the thrust levers to idle. The captain noted that the landing flare began normally but became high at about 15 ft agl. The FO corrected with a shallow descent then a gradual flare. As the aircraft was about to touch down, the captain called for a go-around, believing the aircraft was “running out of flying speed quickly, as the throttles were retarded and the pitch attitude was increasing.” He assumed control, and the airplane touched down firmly with a slight nose-down attitude and thrust at the takeoff/go-around (TOGA) setting.
Post-Landing Events
During the go-around, a loud bang was heard from under the fuselage, and the FO reported an engine failure indication on the electronic centralized aircraft monitor (ECAM). The air traffic control tower (ATCT) reported an engine fire, but the flight crew only observed an engine failure indication. The captain requested a foreign object debris (FOD) sweep of the runway, which found metal and tire debris. A low pass by the tower confirmed all three landing gear appeared down. The crew conducted a visual approach to runway 8, with a normal touchdown. The captain elected to deplane via airstairs rather than evacuation slides, citing no threat to life and the presence of eight wheelchair passengers.
Investigation
On March 16, 2025, the National Transportation Safety Board (NTSB) was notified by Frontier Airlines and began an incident investigation. Parties invited include the Federal Aviation Administration (FAA), Frontier Airlines, the Air Line Pilots Association, International (ALPA), and Pratt & Whitney. An Accredited Representative from the Bureau d'Enquêtes et d'Analyses (BEA) of France was appointed, with Airbus and EASA as technical advisors. Group chairs in operations, human performance, and flight data recorders were assigned. The flight data recorder (FDR) and cockpit voice recorder (CVR) were removed for analysis at the NTSB Vehicle Recorder Laboratory in Washington, DC.
Preliminary FDR data showed the airplane initially touched down on all three landing gear with a maximum recorded vertical acceleration of about 2.2g, exceeding the Frontier Airlines hard landing threshold of 1.8g. Post-incident inspection revealed that the nose landing gear left wheel and tire had separated from its axle. One wheel half fractured, and scratches, gouges, and damage to the tow fitting were noted. Metal fragments from the wheel assembly were ingested by the number one engine, damaging the inlet cowl liner, thrust reverser, fan blades, and guide vanes. The left inboard trailing edge flaps were also damaged. None of the damage met the definition of substantial damage or affected the flight control system.
On May 5-6, 2025, the operational factors group, with assistance from an NTSB Human Performance Specialist, interviewed the flight crew, the Director of Training, and the Director of Operations in Denver, Colorado. The investigation continues.