Secretary of State Tony Blinken couldn't fly back to the U.S. from Davos as planned Wednesday because of a mechanical issue with his airplane, a State Department spokesperson said.

The big picture: The plane Blinken was flying on is a modified Boeing C-40, a U.S. Air Force aircraft assigned to Joint Base Andrews, Rose Riley, a spokesperson for the Air Force said.

• Blinken was in Zurich as of Wednesday afternoon with a replacement Air Force plane on its way, State Department spokesperson Matt Miller said at a press conference. He's expected back in the U.S. on Wednesday night.
• A previously detected oxygen leak made the jet unsafe to fly, per Bloomberg.
• Blinken had been attending the World Economic Forum. The flight issue didn't disrupt any of his meetings, Miller said.

Worth noting: Boeing has faced reputation challenges and cratering share prices following a deluge of bad news concerning its 737 Max jets.

• Boeing did not immediately respond to Axios' request for comment.

Between the lines: This is another bad headline for Boeing, but appears to be unrelated to the issues with the 737 Max.

• The aircraft Blinken was flying on is not a 737 Max, per the Air Force's statement. According to Boeing, C-40 planes are in service at five U.S. air bases and maintained by the U.S. Naval Reserve.
• Boeing 737 Max 9 jets were grounded on Jan. 6 and will remain so until "enhanced inspections" are completed, the Federal Aviation Administration said. Loose bolts were found on the plugged exit doors of several planes.

Editor's note: This story has been updated with details throughout.