UA2255 - Incident: United B739 near Denver on Sep 1st 2025

A United Boeing 737-900, registration N57439 performing flight UA-2255 from Denver,CO to Indianapolis,IN (USA), was enroute at FL350 about 250nm eastnortheast of Denver when the crew decided to return to Denver. On approach to Denver the crew advised they would be able to vacate the runway but requested emergency services to follow them to the gate. The aircraft landed safely on Denver's runway 35L about 80 minutes after departure.

A passenger reported the aircraft had been lining up for departure from runway 25 then the aircraft taxied along the runway, vacated the runway and stopped while the crew was working checklists, the aircraft subsequently returned to the apron. The captain announced that maintenance had found both left and right generators overfilled with oil, maintenance would clear the right generator, so that the flight could go ahead with the APU as second generator. The aircraft departed, about 35 minutes into the flight the crew announced, that the APU had failed and they needed to return to Denver. The aircraft landed without further incident. A replacement aircraft took them to Indianapolis with a delay of nearly 7 hours.

A replacement Boeing 737-9 MAX registration N17550 reached Indianapolis with a delay of 6.5 hours.