SYDNEY - Nearly a year has passed since Malaysia Airlines Flight 370 vanished on a flight from Kuala Lumpur to Beijing, sparking one of the most perplexing mysteries of modern times. Since then, search crews have taken to air, land and sea in a thus-far fruitless hunt for the plane and the 239 people who disappeared with it.

The current phase of the search in the deep, dark and desolate waters of the Indian Ocean has failed to yield a single clue about the plane's fate. Still, despite the lack of fresh leads, the official heading up the search is no less optimistic than when it began.

Here is a look at the latest in the hunt for Flight 370:

Q: How far along is the search?

A: Crews have scoured more than 40 percent of the priority search zone _ a 60,000-square-kilometer (23,000-square-mile) area of the Indian Ocean about 1,800 kilometers (1,100 miles) west of Australia. An international team of investigators who analyzed transmissions between the aircraft and a satellite believe this is where the plane eventually crashed.

Q: How much longer is the search expected to take?

A: Despite occasional delays due to rough weather and equipment snafus, officials believe they're on track to finish searching the priority zone by May.

Q: What happens if they don't find the plane?

A: One option includes expanding the search beyond the priority zone to a wider search area _ an imposing, 1.1-million-square-kilometer (425,000-square-mile) stretch of ocean, says Australian Transport Minister Warren Truss. Exactly how long that would take to complete, and how much it would cost, is unknown.