US aviation giant Boeing has grappled with high-profile production problems and incidents involving its aircraft for more than a year -- leading up to Monday's announcement that CEO Dave Calhoun would step down at the end of 2024.

These are the issues that his successor, who has yet to be named, will be dealing with:

Production issues

Throughout 2023, the aircraft maker was hit by production and delivery delays on its flagship 737 vessel due to manufacturing problems.

In April last year, Boeing reported issues with a supplier part on the 737 MAX that was expected to slow deliveries of the jets.

A few months later, Boeing noted a problem with the aircraft's rear bulkhead, describing the issue as the result of misshapen holes drilled in a part of the fuselage that helps maintain plane pressure.

And in December, Boeing urged customers to inspect for loose hardware on plane rudder control systems after an international operator discovered a bolt with a missing nut while performing routine maintenance.

Safety incidents 

By early 2024, Boeing's production issues spilled into other parts of its operations.

On January 5, a panel known as a "door plug" blew out of a Boeing 737 MAX 9 operated by Alaska Airlines mid-flight, leaving a gaping hole in the cabin.

The affected door plug panel is used to fill an unneeded emergency exit in planes.

The Federal Aviation Administration (FAA) grounded 171 MAX 9 planes and launched an audit into the company's quality control.

A preliminary report by the National Transportation Safety Board (NTSB) published in February found that four bolts securing the panel that blew off were missing.

Boeing employees removed the bolts during an inspection at the Renton plant in Washington state prior to delivery of the aircraft last October.

But Boeing has been unable to produce key information about work performed on the plane before the mid-air scare, according to the NTSB.

Boeing has itself launched an internal investigation and taken steps to improve its safety and quality procedures.

Control failures 

The FAA's audit identified "non-compliance issues in Boeing's manufacturing process control, parts handling and storage, and product control" at Boeing and Spirit AeroSystems.

In a statement dated March 4, the FAA gave Boeing 90 days to outline its action plan to address findings, including from an expert review panel's report examining the company's safety culture.

In 2018 and 2019, two accidents -- off the coast of Indonesia and in Ethiopia -- involving Boeing 737 MAX aircraft claimed 346 lives.

After the latest incident with Alaska Airlines, the FAA halted production expansion of the Boeing 737 MAX as well.

Investigations 

According to US media, in addition to investigations by regulators, the US Department of Justice has also opened a criminal investigation into the January 5 incident.

Last week, the Seattle Times said passengers had received letters notifying them that they had been identified as possible victims of a crime.

Meanwhile, an investigation has been launched in New Zealand after a LATAM 787 Dreamliner dropped violently mid-flight, injuring dozens of travelers.

Heightened scrutiny 

Against this backdrop, incidents involving Boeing aircraft have come under extra scrutiny -- attracting regulators' probes in some cases.

Boeing has noted that several of these other incidents occurred on older aircraft, whose maintenance would be an airline's responsibility.

In mid-January, an Atlas Air Boeing 747 cargo plane made an emergency return to Miami International Airport following an engine problem.

In late February, United Airlines pilots reported that the rudder pedals of the 737 MAX they were flying were stuck after landing in Newark, New Jersey.

Other recent episodes include one in which a United flight headed for Florida returned to the airport it departed from, in Houston, after experiencing an engine fire due to plastic bubble wrap ingested from the airfield.

Another United plane bound for Japan lost a tire after taking off from San Francisco.