Another United Airlines flight has hit a snag, this time with a Boeing 777-200 destined for Paris from San Francisco but diverted to Denver due to engine troubles. According to details released by CBS News, the incident occurred Thursday night and required the plane to land safely at Denver International Airport.

There were 273 passengers on board and 12 crew members, all deplaned normally despite the mid-air scare. No emergency was declared during the landing. However, emergency services were at the ready as a precaution. The Federal Aviation Administration (FAA) said that it will investigate the issue, "United Airlines Flight 990 landed safely at Denver International Airport around 10:55 p.m. local time on Thursday, March 28, after the crew reported a possible mechanical issue." SFist reported that the passengers were still in Denver as of Friday morning, waiting for alternate flight arrangements.

This diversion is part of a series of recent troubling incidents involving United Airlines at San Francisco International Airport, indicating a pattern raising eyebrows. In the past weeks, flights have suffered from mishaps ranging from detached tires to hydraulics problems and, most infamously, a wing flap incident. CBS News highlighted an internal letter from March 22, where United's vice president of corporate safety, Sasha Johnson, seemed to anticipate tighter scrutiny, "Over the next several weeks, we will begin to see more of an FAA presence in our operation as they begin to review some of our work processes, manuals, and facilities," indicating that the airline is bracing for a response from the regulatory body.

Disturbingly, these are not stand-alone instances. A flight as recent as March 7 had its tire falling off, and another on March 8 suffered a hydraulic problem that necessitated an urgent landing in Los Angeles. The series of malfunctions have put United Airlines under a microscope, with the FAA considering "temporary action against United, including some potential restrictions on its ability to add new routes or planes," CBS News reported.