Angelina Jolie's nine-year-old son Knox is learning to fly a plane.

The 42-year-old actress has revealed her youngest son - whom she has with her estranged husband Brad Pitt, with whom she also has 16-year-old Maddox, 14-year-old Pax, 13-year-old Zahara, 11-year-old Shiloh, and Vivienne, Knox's twin sister - has shown a keen interest in becoming a licensed pilot.

Angelina got her pilot's license in 2004 after she was inspired to train while watching planes taking off and landing at an airfield where she and son Maddox used to get lunch, and now it seems that Knox is following in her footsteps.

Speaking in a recent documentary entitled 'The Queen's Green Planet', Angelina said: ''I love being up in the air. I love the freedom. Knox is now learning to fly. It makes me crazy happy to see him discover it. He still needs help with the pedals, but won't for long.''

The 'Maleficent' star was seen in the documentary jetting over the Namibian desert in the pilot's chair of a small plane.

Her comments come after she recently revealed she rarely has time to relax, but doesn't mind as long as she can spend time with her brood.

She said: ''I really don't [relax]. I'm one of those people. It drives me nuts when people tell me to relax.

''I think a lot of moms don't really rest. And somehow we find a real pleasure in that.

''I mean, even if I try to take a bath, I'll end up with at least two of my kids in there with me, which is lovely. I wouldn't trade it at all.''

And Angelina also shared the lesson she believes is most important for her children to learn.

Asked what she teaches her children, she said: ''To value others. If you live life and walk around thinking of yourself and your own needs and desires then not only is it a selfish life, but it ends up being quite an unhappy life, I imagine. And that's where everything goes wrong.

''The wars and hostility, the ugliness and inhumanity in this world comes from this lack of being able to have real empathy for someone else.

''If you can value others, I think things naturally balance out in your own life. When you don't live with ignorant perceptions and that smallness, you open up in a beautiful way.''