Government safety regulators have determined that it could fly for nearly three hours on a single engine in the case of an emergency.
Such government approval has enabled airlines to fly routes such as New York to Hong Kong nonstop on the 777.
Saturday's Malaysia Airlines flight from Kuala Lumpur to Beijing was scheduled to take 5 1/2 hours - one of the shorter routes worldwide for the 777. Malaysia Airlines has its 777s configured to seat 282 passengers with business class and coach cabins.
In addition to its ability to fly long distances and hold a large number of passengers, airlines like the 777 because they can fill its long belly with lots of profitable cargo.
The jet weighs 316,800 (143 tons) pounds empty but is able to carry another 340,000 (155 tons) pounds of passengers, luggage, cargo and fuel. Less than a third of the space in the belly is taken up by luggage.
Boeing has delivered 1,030 of the planes since United Airlines starting flying the first one in June 1995.
There are outstanding orders for another 370. Last year, Boeing announced plans to build a new, larger version of the plane in addition to the four current versions.
