Teaching Your Children About 9/11

I don't think I have to tell any of you that the 10 year anniversary of September 11th is coming up.  But I do need your help.  My son, who is 9, is asking a lot of questions about that day.  We have let him watch a few shows, documentaries, on the events of that day but I'm worried that he will get scared.  The media holds nothing back in their reporting.  There is no easy or nice way to tell the events of that day but I am wondering what you say or don't say to a younger child.  This is the first year he has really asked questions and I think he's old enough to know some of the details.  He is very interested in airplanes and wants to know exactly what happened to each flight but I don't think he understands how many people died on those planes.  I also don't think he understand that those buildings the planes hit were full of people.  I'm just at a loss as to what to tell him and what to keep until he gets older.  I am hoping that some of you out there in the blog world have had this type of discussion with your child and can give me some advice.

Thanks in advance!