* Alexandre de Juniac seen taking the reins
* Spinetta was brought back as head in 2011
* Union says a succession plan may be announced soon
PARIS, March 21 (Reuters) - Air France-KLM Chief Executive Jean-Cyril Spinetta plans to quit nine months before the scheduled end of his mandate, website La Tribune reported on Thursday.
Spinetta's resignation would pave the way for Alexandre de Juniac, head of the group's Air France unit, to take the reins at the parent company, the site said, citing unnamed sources.
An Air France spokeswoman declined to comment.
Spinetta, the architect of the 2003 Air France-KLM merger who led the group until 2009, was brought back to lead the Franco-Dutch airline in late 2011 in a move designed to speed up restructuring.
The Air France pilots' union said in a statement that a succession plan may be announced "soon", without confirming the report.
La Tribune said Spinetta planned to announce the move to Air France-KLM's board on Monday.
Spinetta must step down by the company's 2014 annual shareholder meeting, when he will have hit the company's mandatory retirement age of 70.