What: Oman Air Boeing 737-800 en route from Muscat to Chennai
Where: Mumbai
When: May 25, 2009
Who: 140 passengers
Why: When a passenger found a suspicious object and a letter which threatened to kill all the passengers aboard the flight, the crew requested an emergency landing.
Another source quoted: ‘a flight attendant had found a note in one of the lavatories saying “you will all die. Bye.”‘
The flight landed safely and the passengers were directed to another plane.

Virgin Atlantic flight VS-107 had to return and make an emergency landing at Heathrow Airport, London, England, on April 27th.
Eastar Jet flight ZE-623 made an emergency landing at New Chitose Airport, Japan, on September 1st.
Etihad Airways flight EY-73 made an emergency landing in Zurich, Switzerland, on June 18th.