How can a plane carrying 239 people just disappear over the ocean for more than three days?
As puzzling as it sounds in this age of modern technology, what happened to Malaysia Airlines flight MH370 is not the first reminder of how vast the seas are and how difficult it is to locate something lost in them, said a report by the AP news agency.
It took two years to find the main wreckage of an Air France jet that plunged into the Atlantic Ocean in 2009.
It also took a week for debris from an Indonesian jet to be spotted in 2007 after it crashed near the area between Malaysia and Vietnam where Saturday's flight vanished.
Today, the mostly intact fuselage still sits on the bottom of the ocean.
"The world is a big place," Michael Smart, professor of aerospace engineering at the University of Queensland in Australia, told AP.
"If it happens to come down in the middle of the ocean and it's not near a shipping lane or something, who knows how long it could take them to find?"
To add to the confusion, officials had said that MH370 might have made a turn back towards Kuala Lumpur, making it even more difficult to find as it might have been hundreds of kilometres from where it last made contact with air traffic controllers.
Aviation experts say the plane will be found — eventually. Since the start of the jet age in 1958, only a handful of jets have gone missing and not been found, the AP report said.
"I'm absolutely confident that we will find this airplane," Captain John M. Cox, who spent 25 years flying for US Airways and is now CEO of Safety Operating Systems, was quoted as saying.