ABU DHABI— An Etihad passenger flight from Abu Dhabi to Moscow had to make an emergency landing at a central Russian airport close to the Black Sea for “operational reasons”.

A United Airlines flight made an emergency landing in Denver this morning.United flight 867 was en route from Toronto to San Francisco when the pilot noticed some engine vibrations, said Rahsaan Johnson, a spokesman for the airline.

A United Airlines flight from Washington, D.C., to Cancun made an emergency landing Monday at Tampa International Airport due to mechanical problems.