CHICAGO — United Airlines said Thursday that federal regulators are letting it resume planning for growth after they imposed restrictions on the airline following a series of flight mishaps earlier this year, including an engine fire and a tire falling off a plane.

United said the Federal Aviation Administration “has allowed us to begin the process of restarting our certification activities, including new aircraft and routes.”

The FAA indicated, however, that it has not made any final decisions from its review of the airline, which began in March.

“The FAA has not approved any expansion of United Airlines’ routes or fleets,” an agency spokesperson said in a statement. The FAA said its review of the airline “is ongoing, and safety will determine the timeline for completing it.”

The FAA is insisting on being present when United personnel make final inspections of new planes that replace older ones.

In a memo to employees, United said the ability to resume planning for growth was “good news,” but it noted that FAA inspectors were still reviewing the airline's work processes, manuals and facilities.

The FAA increased its oversight of Chicago-based United after a series of flight problems.

In one, a piece of aluminum skin fell off a plane flying from San Francisco to Oregon. Another plane lost a tire after takeoff from San Francisco, and another suffered an engine fire in Houston.

Pilots reported that rudder pedals used to steer on the runway failed after landing in Newark, N.J., and another plane rolled off a taxiway in Houston.

The incidents led United CEO Scott Kirby to assure customers the airline was safe.

Kirby said the events were unrelated but they "have our attention and have sharpened our focus.” He said United would review each incident to see if changes were needed in safety training and procedures.