By Amy Schellenbaum
March 09, 2015
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Credit: © Asyraf Rasid/Demotix/Corbis

On March 8, 2014, Malaysian Airlines flight MH370 vanished from radar and radio, its 227 passengers and 12 crewmembers presumed dead. In the last year, many have attempted to unearth where, exactly, the missing plane ended up, and how, exactly, a Boeing 777 completely dissipated. Answers, even after 366 days and countless international investigations, are still largely nonexistent.

Yesterday, the day of the one-year anniversary of the plane's disappearance, transit authorities released a 585-page interim report, and while it doesn't provide much insight into where the plane went or why it went missing, it does a little to explain why its disappearance is such an unknown.

According to the report, the battery powering an underwater locator beacon—that is, a device on the plane activated by water immersion—had expired in 2012, with no signs of it having been replaced. Put another way: a device used to record data about the plane very well could have been less effective, or even not working at all. The report said the battery could have worked beyond its expiration date, but that the failure to replace it was an "oversight not noted until after the disappearance of MH370, when details were requested."

Other than that, the report found the plane to be "airworthy" at the time of its takeoff, with no alarming notes in recent maintenance records.

There were also no concerns raised about the pilot or other crewmembers, even after an international cohort of investigators dug deep into the backgrounds of each crewmember (read: psychological, financial, and personal profiles).

The full report is this way.

Amy Schellenbaum is the Digital Editor of Travel + Leisure. Follow her on Twitter at @acsbaum.