Keep him away from the news for a week or so before-at least as much as you can. (Just in case there are plane crashes).
Also, not sure how he reacts with more info, but maybe you can talk with him about the safety stuff on the planes? ie, life jackets, emergency slides, etc. Some kids would do better knowing about all the safety stuff, some would freak out even knowing that any of it might be necessary.
And...some therapy might be helpful. you have plenty of time for that.