Frontier Airlines Flight 3506

On April 15, 2025, about 2140, Atlantic daylight time (ADT), Frontier Airlines, flight 3506, an Airbus A321-271NX, N607FR, sustained nose wheel and engine damage during an attempted landing at the Luis Munoz Marin International Airport (SJU), San Juan, Puerto Rico. The 235 passengers and crew onboard were uninjured. The flight was operated as a Title 14 Code of Federal Regulations Part 121 scheduled domestic passenger flight from Orlando International Airport (MCO), Orlando, Florida to SJU.

According to the flight crew, the first officer (FO) was the pilot flying, and the captain was the pilot monitoring during the night flight to SJU. 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) on approach to runway 10.

An aural RETARD alert is designed to occur at a radio altitude (RA) of 20 ft on manual landing to advise the flight crew to reduce the thrust levers to idle. The FO recalled that during the approach, she brought the thrust levers back to idle at 20 ft RA while the RETARD aural alert sounded.

The captain recalled that the landing flare began normally but became high at about 15 ft RA. The FO stated that around 15 ft RA, the captain noted that the aircraft was too high, so she corrected with a shallow descent and then a gradual flare. As the aircraft was about to touch down, the captain called for a go-around. The captain stated that he believed the aircraft was “running out of flying speed quickly, as the throttles were retarded and the pitch attitude was increasing” so he assumed control. He recalled that the airplane was slightly nose down with the thrust at the takeoff/go-around (TOGA) setting when the airplane then touched down firmly.

The captain stated that during the go-around, they heard a loud bang coming from under the fuselage and the FO called out that an engine failure was displayed on the electronic centralized aircraft monitor (ECAM) display.

The air traffic control tower (ATCT) controller reported an engine fire, but according to the flight crew, they only had an indication of an engine failure. Unsure of the damage sustained, the captain asked for a foreign object debris (FOD) sweep of the runway and a description of any debris found. Some metal and tire debris were found on the runway and reported to the flight crew.

The captain stated that he flew a low pass by the ATCT to see if the controllers could determine if all three landing gear appeared to be down. The ATCT controller reported that the landing gear was intact, and the flight crew prepared for a visual approach to runway 8. At touchdown, the airplane behaved normally so the captain elected to clear the runway and set the parking brake as the fire department approached to inspect the number one engine for any fire. No fire was present, and the captain elected to coordinate for airstairs to deplane the aircraft rather than using the evacuation slides. He felt there was no threat to life and the slides posed a greater danger to passengers than the airstairs. He also noted that there were 8 wheelchair passengers on board. The passengers were unloaded via airstairs and bussed to the terminal.

Investigation

On March 16, 2025, the National Transportation Safety Board (NTSB) was notified by Frontier Airlines about the event and, in response, began an incident investigation. As part of the investigative process, the NTSB invited qualified parties to participate in the investigation. These included the Federal Aviation Administration (FAA), Frontier Airlines, the Air Line Pilots Association, International (ALPA), and Pratt & Whitney. In accordance with the provisions of Annex 13 to the Convention on International Civil Aviation, an Accredited Representative from the Bureau d'Enquêtes et d'Analyses (BEA) of France, the State of Design and Manufacture of the airplane, was appointed to support the investigation, with Airbus and EASA as technical advisors.

NTSB group chairs in the areas of operations, human performance, and flight data recorders were assigned. The flight data recorder (FDR) and the cockpit voice recorder (CVR) were removed from the airplane and shipped to the NTSB’s Vehicle Recorder Laboratory located in Washington, DC, for analysis. A preliminary review of the FDR has been completed and a plot showing several parameters is shown in figure 1. The data revealed that the airplane initially touched down on all three landing gear with a maximum recorded vertical acceleration of about 2.2g. This value is above the hard landing threshold of 1.8g per Frontier Airlines aircraft maintenance manual (AMM) Chapter 5 limitations.

Figure 1. Plot of the FDR data from the event landing.

A post incident inspection of the airplane revealed that the nose landing gear (NLG) left wheel and tire had separated from its axle and departed the aircraft after the initial hard landing (figure 2). One of the wheel halves had fractured and there were numerous scratches and gouges noted on the NLG along with damage to the tow fitting. Metal fragments from the wheel assembly appear to have been ingested by the number one (left) engine and damage was found on the engine's inlet cowl liner, thrust reverser, fan blades, and guide vanes. The left inboard trailing edge flaps were also damaged. None of this damage met the definition of substantial damage or affected the flight control system of the airplane.

On May 5-6, 2025, the operational factors group, with assistance from an NTSB Human Performance Specialist convened in Denver, Colorado. The group interviewed the Frontier airlines flight crew, the Director of Training and the Director of Operations.

Figure 2. Nose landing gear with its left wheel missing (Source: Frontier Airlines)

In January 2021, an article titled “A Focus on the Landing Flare” was published by Airbus in their Safety First magazine. The article analyzes two case studies to highlight operational pitfalls and reinforce best practices during the flare phase of landing. You can read the full article on Airbus’s official Safety First website here: A Focus on the Landing Flare.

The investigation continues.

Verbatim NTSB factual narrative from the NTSB dataset