On Saturday March 8, at 12:41 AM, Malaysia Airlines Flight 370 took off from the Malaysian capital of Kuala Lumpur, and headed to Beijing. Seven hours into the flight the Boeing 777-200ER disappeared and, along with it’s 239 passengers, has been missing ever since.

Over the last week experts have been reconstructing key moments in the flight, trying to find out where, when, and why things went wrong. When the plane took off all tracking systems were functional.

However shortly after departure one of the communication systems was turned off. Although it remains unclear exactly when the Aircraft Communications Addressing and Reporting System or ACARS was turned off, Prime Minister Najib Razak mentioned that the system was turned off just before the plane crossed the Malaysian peninsula.

The ACARS is a system that collects information on the performance of the plane for review. It’s similar to computers that track the oil levels and tire pressure in cars. ACARS is a big deal according to CNN aviation and airline correspondent Richard Quest. “Your boss will know how you’ve flown the plane because ACARS will have told them,” Quest said.

The fact that such a vital and complex system was shut off points to an inside job. Quest implied that turning of ACARS is a difficult feat that not anybody can do. This information raises alarming questions about the pilots of flight 370 and their involvement in the disappearance of the plane.

Around 1:30 AM the planes transponder was shut off. The transponder regularly sends out an electronic signal, giving information about the planes flight number, speed, height, and heading. This is extremely useful to air traffic controllers, allowing them to view all relevant information as a series of blips on a screen. At this point the plane is flying blind somewhere between Malaysia and Vietnam.

At about the same time the transponder was turned off someone in the plane’s cockpit made a voice check-in with air traffic controllers as the airliner was apparently leaving Malaysian airspace and entering Vietnamese airspace. Whoever made the voice check-in used the correct radio parlance of “good night”, used when executing a handover from one airspace to another, according to Zulazri Mohd Ahnuar a Malaysian civil aviation officer.

The airliner’s last know location was found at 8:11 AM, when the plane was on the wrong side of the Malaysian peninsula, 400 miles off course. Where flight 370 is now, 7 days later, remains a horrible mystery.