Sources say the Federal Aviation Administration is considering interim action against United after a series of aviation mishaps

The Federal Aviation Administration is considering potential temporary action against United Airlines beyond what was described in a letter the company sent to employees on Friday, two sources familiar told CBS News.

This comes in response to A series of disturbing events Involving United aircraft over the past month which included The rush of his descent Boeing 777, and Fly plate Old Boeing 737 plane.

Among the potential temporary measures discussed was preventing United from launching new routes for which it has not yet begun selling tickets. Another matter to be considered is allowing the carrier to continue acquiring new aircraft — while temporarily halting its ability to bring new aircraft into revenue service, which refers to commercial flights carrying paying passengers.

A third possibility is to temporarily disallow United pilots from certifying new captains. Airlines usually do these signings internally.

Sources stress that discussions within the FAA may not lead to action, so some or all of these actions may never come to fruition. United says it has not been notified of the final decision by the FAA, and internal FAA discussions may be ongoing.

“Due to recent safety events, the FAA is increasing oversight of United Airlines to ensure it is complying with safety regulations, identifying and mitigating hazards, and managing safety effectively,” the FAA said in a statement provided to CBS News on Saturday. “Ongoing certification activities may be permitted to continue, but future projects may be delayed based on oversight findings. The FAA will also begin evaluating United Airlines under the provisions of the FAA. Certificate holder evaluation process“.

In an interview with NBC News this week, FAA Administrator Michael Whitaker acknowledged that he spoke last weekend with United CEO Scott Kirby about recent events.

“I know they're taking some aggressive measures and looking into these cases,” Whitaker told NBC News. “We'll look at each one of these incidents and see if we see a pattern… He's concerned, I'm concerned, no one likes to see this spike in incidents. So we're both doing our work to look at where those risks might be.”

In a letter Friday to employees, Sasha Johnson, United's vice president of corporate safety, seemed to acknowledge that some temporary measures were in place.

“Over the next few weeks, we will begin to see more of an FAA presence in our operations as they begin to review some of our work procedures, manuals, and facilities,” Johnson wrote. “As part of this effort, the FAA will also pause a variety of certification activities for a period of time. These activities will vary depending on the work group and we will learn more from the FAA about that soon.”

The FAA's potential temporary action was first reported by Bloomberg.

“Safety is our top priority and is at the heart of everything we do,” Kirby wrote. In a message To customer sent on March 18th. “Our team reviews the details of each case to understand what happened and uses those insights to guide our safety training and procedures across all employee groups.”

United has aggressive growth plans, including hundreds of new aircraft on order, and is rapidly developing its international route map. Earlier this month, United announced plans to launch service to Marrakesh, Morocco, Cebu, Philippines, and Medellin, Colombia.

In the same March 7 announcement, the airline said it plans to increase its flights to Hong Kong, Seoul, South Korea, Porto, Portugal, and Shanghai, China.

The pause on route expansion and the introduction of new aircraft will likely have a significant impact on United's bottom line, which has already been affected by ongoing delivery delays from Boeing.

Sources at the airline were unable to say when this “pause” would begin, or what specifically would be paused.