(Reuters) - Boeing Co BA.N unveiled a fourth straight quarterly loss and deeper job cuts on Wednesday as the coronavirus pandemic and the lengthy grounding of its 737 MAX continued to hammer revenue.The U.S. planemaker also said it was sticking with reduced production rates announced in July, and signaled it was ready to cut 787 production again if needed with 50 undelivered jets sitting outside its plants. Shares in Boeing fell 4.6%, lagging weaker U.S. markets. The COVID-19 pandemic has sharply reduced air travel, pushing some airlines to bankruptcy or forcing them to seek government aid and delay taking jets. As a result, Boeing has slashed production and shed thousands of jobs while also working to emerge from a 19-month-old worldwide 737 MAX ban triggered by two crashes. Chief Executive Dave Calhoun told employees Boeing now expects to eliminate some 30,000 jobs to reach a workforce around 130,000 by end-2021. That is 11,000 more than previously discussed, with 7,000 extra posts disappearing through increased voluntary or involuntary layoffs and the rest through attrition. Calhoun predicted airline traffic would end the year at around 30% to 35% of 2019 levels, with a return to pre-pandemic levels in about three years. He also raised the prospect that stricter certification rules following the 737 MAX grounding would further delay its new 400-seat 777X.