I was able to zoom in as planes landed and you can see the pilot 's faces as they were landing
How is the auto focus?
I am not a professional photographer, it is a hobby.  I had a telephoto zoom lens on an old Canon AT-1 film camera but I haven't used that camera in many years.  I was amazed at how close this telephoto lens got to the subject.  The day I got the lens I went to shoot a building in town for the webpage.  I put the EF-S 55-250mm lens on the camera and walked the three blocks to the building.  I could not get the building in the frame without crossing the street and introducing traffic and traffic lights into the picture.  I used  the kit lens (EF-S 18-55 mm) and got the shot.  I have used the lens at a Fly-In at the local airport.  I was able to zoom in as planes landed and you can see the pilot's faces as they were landing.  Also you could get great shots of the aircraft taking off and get several shots  after they were in the air.  The shots were always sharp no matter how far the subject was away from the camera.  I remember from the old AT-1 zoom, the further the object was away from the camera the more a tripod was needed.  Not with this lens.  The IS worked very nicely and every shot was sharp.  I would recommend this lens. 