London, Feb 19 : `The O. C.' star Rachel Bilson and beau Hayden Christensen may soon announce their engagement, as the actress was spotted with a huge rock on her wedding finger.

Rachel, who has been dating Hayden for a year after the duo met on the sets of `Jumper', was spotted with ring while she was in flight going to New York, reports PageSix.

"A man sitting in front of her on the plane saw a ring on her finger and asked if she was married," The Daily Express quoted a source, as saying.

To which Rachel replied: "I''m not married yet, just engaged. I know I look like I''m 15 but I''m actually 27." (ANI)