I just wanted to point out that "the most realistic on the block" title is held by the PMDG 747-400 pax and freighter, with the LDS a close second.But since this person is new to the hobby, I suggest freeware airplanes as a good start

>Firstly, I'm looking to add more traffic to the airport. Not>so much of the default Airlines, more real-life Airlines like>'Alitalia' etc. Is there anyway that this can be done?http://www.projectai.com/ (freeware AI traffic library)http://www.world-of-ai.com/ (another one)They provide quite easy to use installers, so adding new AI flight plans isn't that hard.Of course, there are also payware add-ons which were already listed in this thread.>Secondly, I'm after some more Aircraft to fly apart from the>default ones already in FS2004. I'm not to good with computers>so are there any Aircraft which come with the Panel, Sound,>Lights, Textures etc aready in the file? Like a 'full>packaged' Aircraft so I don't have to spend too much time>messing about with different files etc. I'm into Commercial>Passenger Aircraft. I've had a look on the File Libary but I'm>not too sure what I'm looking for... Is there any 'full>packaged' Aircraft which you can recommend?As for freeware - I can highly recommend the iFly 747-400 - a very feature rich Boeing 747-400 with a complete panel (including virtual cockpit), very well modeled systems and a 300+ pages manual. This is a complex package, but it really comes very "complete" so you just download and install it. It will keep you busy for a while, but you will have to learn a lot.It can be found in the file library here at avsim, just do a search for IFly 747 and you will find a number of files related to this product.As for payware airliners. There are lots of very good packages. PMDG, Level-D and PSS seem to be the most popular producers of good quality addons. You can get everything from a B737 up to a 747-400. Links were already posted here.