Pressures in a plane

Today, my friend told me about an experience she had when flying. She had bought a bag with coffee beans from Starbucks before she got on the plane.  She put it inside her suitcase, which travels in the bottom of the plane.  When she arrived to Bulgaria and got the bag out of her suitcase, the coffee bag was "stuck" to the coffee beans.  All the air had left the bag.  This happened because of the pressure gradient in the plane.  Pressure at such a high altitude is lower than pressure at sea level.