(Photo: Splash Photo Agency)

Known for keeping their romance low-key, Rachel Bilson and Hayden Christensen quietly got engaged over the holidays.

A pal told People.com that the two are “so excited” and have yet to set a wedding date. According to PageSix, Bilson reportedly told a man on a flight from Los Angeles to New York that she’s “not married yet, just engaged.”

A rep for the couple told RadarOnline: “I don’t comment on my client’s lives.”

Still, a picture’s worth a thousand publicists’ spin! On the alleged flight, Bilson was spotted wearing a sparkling diamond ring.