Boeing lost $26.6 billion in market value since Sunday's 737 Max 8 crash

Boeing investors lost $26.6 billion in the first two trading days this week following the deadly crash of one of its popular 737 Max 8 jets in Ethiopia.

Boeing's shares slid 11 percent from $422.54 Friday to $375.41 at Tuesday's close before turning positive Wednesday morning. The share slide cut its market value from $238.7 billion to $212.1 billion over Monday and Tuesday as international aviation regulators and airlines moved to ground 737 Max jets from China to Mexico.

Edward Jones downgraded Boeing's stock to hold from buy, noting a possible "delay in orders."

Sunday's crash of a passenger jet en route from Addis Ababa to Nairobi killed all 157 people on board. The disaster came five months after a Lion Air 737 Max 8 crashed in Indonesia, killing all 189 people aboard. The cause of the Ethiopian Airlines plane is under investigation.

The U.S. is increasingly alone in defending the American-made jets since the Federal Aviation Administration deemed the 737 Max to be "airworthy" earlier this week. The aircraft hasn't been grounded in the U.S.