You can search the video that you want on youtube (passing aircraft / taking off, landing and e.t.c)
and download it using Youtube Downloader
YouTube Downloader - Free software downloads and software reviews - CNET Download.com
there is a function on Youtube Downloader that you can convert video to to mp3 file
If you want to get the timing of the sound that you want, you can download this Audio Editing tool.
Audacity: Free Audio Editor and Recorder
All of this software are using a user friendly interface. that is why it was very easy to learn and used this tools.
I used the audio that I edited for personal used only.