The crew of the A321 airplane that crashed on the Sinai Peninsula did not report plane malfunction to the tower, a source with knowledge of the situation told Interfax in Cairo.

"According to the updated information, the captain did not make a distress call, did not report malfunction and did not ask for emergency landing," the source said.

In his words, the airplane capsized in its fall.

"The plane fell on its back; it actually fell on its back. Nevertheless, it would be premature to suggest any theories. Participants in the inquiry have not produced any theories of this event as of yet," the source said.

He added that the testing of the plane's 'black boxes' would begin on Monday.

"The testing of the 'black boxes' will begin on Monday morning, and it will be possible to assess their condition when this is done," the source said.