Boeing ( BA ) shares slumped on Tuesday after the jet maker reported deliveries fell by more than half in May compared with the year before, as the firm continues to grapple with the fallout of January’s door-plug blowout.

Boeing’s order volume declined significantly in May. The company received just one new order for four jets last month, compared to seven planes across three orders in April. Its backlog declined to 5,625 from 5,646 in April.

Deliveries Down As 737 Max Fallout Continues

The 737 MAX is Boeing’s best-selling plane, but the Federal Aviation Administration (FAA) in January barred the company from increasing production of the model after an Alaska Airlines flight lost part of its fuselage mid-flight. The FAA and Department of Justice both launched investigations into Boeing shortly thereafter. The FAA is also overseeing the development of a plan to overhaul Boeing’s safety and quality control standards.

Boeing delivered 24 planes last month, down from 50 in May 2023. Nineteen of those aircraft were 737 MAX jets, three more than in April but 16 fewer than in the prior year. Meanwhile, Airbus ( EADSY ), Boeing’s largest competitor , delivered 53 planes last month and received orders for 27.

Boeing shares were down almost 2.4% at nearly $186 as of 3:10 p.m. Eastern Time Tuesday. They have lost nearly 30% of their value so far this year.