Ethiopian Airlines-bsp-bb-link> agreed to buy as many as 20 of Boeing Co. ’s massive 777X aircraft, providing the coming jet with an important endorsement from one of Africa’s premier airlines. Mesfin Tasew-bsp-person>, chief executive officer of Ethiopian Airlines Group, unveiled the latest deal Tuesday in Addis Ababa. The airline placed a firm order for eight 777-9, along with options for another 12 of the hulking jetliners, designed to seat more than 400 travelers. The deal — with a value of about $11 billion, Tasew said — provides some sales momentum for Boeing as it works to complete certification of ...