Rachel McAdams cries on aeroplanes because of the "altitude".

The actress' new movie is called The Vow, and follows a young woman who loses her memory and has to fall in love with her husband all over again.

The film has made people cry and Rachel admits she can often be found in tears when at the cinema.

"I can be quite surprised by what makes me cry. Usually it's quite spiritual things. Darren Aronofsky's The Fountain made me cry. I watched it in a theatre and the person beside me was laughing and I was bawling, so I like the kind of movies where it sneaks up on you. But I cry quite easily, especially on aeroplanes. I think it's the altitude," she laughed.

Channing Tatum appears alongside Rachel in The Vow. The hunk flashes some flesh in one scene and Rachel is glad her character had to be shocked as she couldn't believe what she was seeing.

"Thankfully, I don't think I had lines in that scene. I just had to scream so it was perfect!" she laughed to Look magazine.