mh370, page-132

from Wikipedia 'diego garcia' :

ETOPS emergency landing site
Diego Garcia may be identified as an ETOPS (Extended Range Twin Engine Operations) emergency landing site (en route alternate) for flight planning purposes of commercial airliners. This allows twin-engine commercial aircraft (such as the Airbus A330, Boeing 767 or Boeing 777) to make theoretical nonstop flights between city pairs such as Perth and Dubai (9,013.61 km or 5,600.80 mi), Hong Kong and Johannesburg (10,658 km or 6,623 mi) or Singapore and São Paulo (15,985.41 km or 9,932.87 mi), all while maintaining a suitable diversion airport within 180 minutes' flying time with one engine inoperable.