Tarik,
I have had a similar problem in the past when my Internet connection was broken during the download. The problem is that this broken file is kept in your PC's memory and when you try to download it again, the PC finds that file in your Temporary Internet Files and thinks "I've got this already" so it stops the download.
To avoid this, you must clear out your Temporary Internet Files folder (look under Control Panel/Internet Options) and delete all the contents, then you MAY be able to download the planes from scratch...
This worked for me so it's worth a try - if it doesn't work, let us know here and we can try and suggest something else
