Boeing 737 Max 9 groundings hit United, Alaska following blowout

A United Airlines Boeing 737 Max airplane takes off in the rain, Wednesday, Dec. 11, 2019, at Renton Municipal Airport in Renton, Washington. Alaska and United are the only U.S. airlines that fly the Max 9 variant that has been grounded. (Associated Press)

Alaska Airlines and United Airlines grounded all of their Boeing 737 Max 9 jetliners again on Sunday while they waited to be told how to inspect the planes to prevent another inflight blowout like the one that damaged an Alaska jet.

Alaska Airlines had returned 18 of its 65 737 Max 9 aircraft to service Saturday, less than 24 hours after part of the fuselage on another plane blew out three miles above Oregon.