NEW DELHI—The international search for the Malaysia Airlines Flight 370 widened and moved drastically farther west into the Indian Ocean as new information showed the plane likely remained airborne for hours after it blinked off radar screens last weekend.

Indian aircraft and ships began fanning out a day ago around the Andaman and Nicobar Islands, a distant Indian territory toward the coast of Myanmar, and across more than 13,000 square miles of open sea.

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