KUALA LUMPUR, Malaysia (AP) — Malaysian Prime Minister Najib Razak has called for real-time tracking of planes and improvement to communication systems to prevent a repeat of the mysterious disappearance of Flight 370.

In an opinion piece Wednesday in the Wall Street Journal, Najib urged the global aviation industry to make changes that would "make it harder for an aircraft to simply disappear, and easier to find any aircraft that did."

He said "real-time tracking of commercial planes is long overdue."

The Malaysia Airlines plane carrying 239 people was traveling from Kuala Lumpur to Beijing on March 8 when it disappeared.

The search coordination center says an Australian ship carrying a robotic submarine returned on Monday to part of the Indian Ocean near where underwater sounds were heard last month.

Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.