Aviation was his "passion", his sister Renee told French radio station RTL.
"Since he was very young, it was his dream to be a pilot and the dream came true. He had been in Indonesia for three years...He was a very good pilot, an excellent one," she said.
Flight QZ8501 disappeared over the Java Sea yesterday and a top official warned today that the Airbus A320-200 was likely at the bottom of the sea.
She said she last spoke to him on Friday over the Internet. He told her he had spent an enjoyable Christmas and was heading off to work the next day.
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"We want them to find the plane, to explain to us what happened and to know whether we can go there, myself and my mother," said Renee.
The co-pilot's mother, Rolande Peronet-Plesel, told rolling news channel BFMTV that she received the call every parent dreads at 3:00am, from her son's girlfriend.
"I'm waiting but we're used (to planes going down) and not finding people. They have never found the last plane that went down in the same place," she said, in an apparent reference to missing Malaysia Airlines MH370.