March 25 (Reuters) - Boeing's David Calhoun will step down as CEO at the end of 2024, capping four turbulent years at the helm as the iconic planemaker seeks to address a spiraling safety crisis following a mid-air panel blowout on a 737 MAX plane in January.

Calhoun, previously Boeing's chairman, was tasked with steering the aerospace giant through the turmoil sparked by two deadly crashes that led to the grounding of its best-selling 737 MAX jetliner.

However, the company struggled to shake off production issues and safety concerns during his tenure, frustrating its airline customers and sparking heightened scrutiny from U.S. regulators, as well as lawmakers.

Here are some of the issues Boeing faced:

PRODUCTION, SAFETY CHALLENGES

* Calhoun took charge when the planemaker was looking to bounce back from back-to-back crises - first over the two MAX crashes in 2018 and 2019 that killed 346 people and then the pandemic - which saddled it with $38 billion in debt.

* In 2021, it halted 737 MAX deliveries after electrical problems re-grounded part of the fleet, while shortages of a wiring connector slowed production in 2022.

* Last year, a quality problem at supplier Spirit AeroSystems forced it to halt deliveries of some 737 MAX jets.

* This year, U.S. regulators temporarily grounded 171 MAX 9s jetliners for safety checks following the cabin panel blowout on the Alaska Airlines jet.

* The Federal Aviation Administration in February limited Boeing's 737 production to 38 a month and gave it 90 days to develop a comprehensive plan to address quality.

* Earlier this month, an audit by the regulator found multiple instances of Boeing and Spirit AeroSystems failing to comply with quality control requirements.

* Reuters reported last month Boeing's quality division had atrophied in recent years as many experienced inspectors left during the pandemic and amid the pressure to stick to the production recovery schedule.

* Boeing is in talks to buy its former unit Spirit, which it spun off in 2005, to get more control over its supply chain.

ROCKY SHARE PERFORMANCE

Boeing's stock has lost nearly 43% of its value better since Calhoun took the top job on Jan. 13, 2020. Meanwhile, rival Airbus has added more than 26% to its market capitalization during the same period.

AIRBUS TAKES MARKET SHARE

Airbus has been steadily growing single-aisle market share with its A320 jet family in the wake of multiple crises involving the MAX.

As of February, Boeing has delivered 54 airplanes, including 42 MAX jets, in the first two months of 2024, down from a total of 66 reported in the same period last year.

(Reporting by Aditya Soni, Arunima Kumar and Sourais Bose in Bengaluru)