CHICAGO (AP) — Federal regulators are increasing their oversight of United Airlines, the company announced Friday, following a series of recent issues including a piece of the outer fuselage falling off one jet, an engine fire and a plane losing a tire during takeoff.

United’s vice president of corporate safety, Sasha Johnson, said the Federal Aviation Administration will examine “multiple areas of our operation” to ensure safety compliance.

“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,” she said in a note to employees. “We welcome their engagement and are very open to hear from them about what they find and their perspective on things we may need to change to make us even safer.”

Johnson said the FAA will pause certification activities but did not provide details.

The agency said it “routinely monitors all aspects of an airline’s operation” and did not describe any additional steps it is taking in United’s case.

In a statement, an agency spokesperson said FAA oversight “focuses on an airline’s compliance with applicable regulations; ability to identify hazards, assess and mitigate risk; and effectively manage safety.”

Earlier this week, FAA Administrator Mike Whitaker told NBC News, “We are going to look at each one of these incidents and see if we see a pattern. … No one likes to see this spike of incidents.”

Whitaker said he spoke with United CEO Scott Kirby about the events.

Separately this week, Kirby tried to reassure customers that the airline is safe, saying that the recent issues were unrelated to each other.

Kirby said the airline was already planning an extra day of training for pilots starting in May and making changes in training curriculum for newly hired mechanics and that it would consider additional changes.

Among the most recent issues, a chunk of outer aluminum skin was discovered to have fallen off the belly of a United Boeing 737 after it landed in Oregon. Earlier this month, a United jet suffered an engine fire during takeoff from Houston, and a tire fell off another United jet as it left San Francisco.

Other problems included a hydraulic leak and a plane veering off a taxiway and getting stuck in grass.

United is the nation’s second-largest airline by revenue, behind Delta Air Lines.