Click here for the official Frankfurt Airport flights arriving to Frankfurt list. Here you'll see just how many inbound flights are landing in Frankfurt every day.
Note: Do not confuse Frankfurt Airport with Frankfurt Hahn Airport, which is used by mostly budget airliners, like Ryan Air.
When you're flying into Frankfurt , on the descent, if the wind is blowing from the east your aircraft will have to line up to Frankfurt Airport on a path that hopefully gives you a good look Westward at Frankfurt itself. Look out to the right of your jet (personal jet if you've got one) and you may see a few skyscrapers, the River Main, and the landscape around the city.
If you're unlucky, your view will be blotted by banks of clouds, but don't let that deter you from peering out the window: As your aircraft decreases speed and lines itself up to the runway, you may see a forest below. That is the State Forest, a massive open forest between Frankfurt Airport and Sachsenhausen.
In partial answer to the question of why is Frankfurt an international airport there is a one word answer: Zeppelins. In the 1930s Zeppelins launched from Frankfurt. While this doesn't entirely account for the transgression of Frankfurt Airport to what it is today, it does help explain the origins. Also of historical note is the Berlin Blockade; much of Allied Air Caro lifted off from Frankfurt Airport. Frankfurt airport began in the 1920s and has since grown, including being connected to the ICE network, and having the US move out of their air base in 2005, therefore freeing up space. You can read the official timeline of Frankfurt Airport's History.
In our modern times, the establishment of Frankfurt Airport as a major transport hub for travellers and cargo could be down to a few very important factors:
Somewhere in Germany, and indeed Europe, there needs to be a major international airport for import and export, and due to the increasing demands on airports (less noise, less flights, less take-off and landing times, shrinking flight-corridors) it's hard to build new airports, and hard to expand existing airports. The emphasis is then on maximising the capacity of existing airports - Frankfurt falls into this capacity. Other European major airports like Heathrow (UK) and Charles De Gaul (France) face the same hurdles as Frankfurt.
For cheap deals on flights out of Frankfurt , if you don't mind your lack of choice for a destination, you can go to Frankfurt Airport with your bags packed and find the Airlines that offer cheap flight tickets of the day. This is ideal for adventurous wanna-be jet-setters who need to clock up some Air Miles and bragging rights that they can dine out for years to come. However, the downside is, the only destination options may be all the boring places everyone before you has been a thousand times.
If you have a few hours to wander Frankfurt Airport you want be doing anything authentically German except for drinking the local beer and reading the local newspapers.
If you have a perhaps a minimum of four hours, you can take an S-Bahn into Frankfurt (30 minutes travelling time, get off at Konstablerwache or Hauptwache ) and head south into Frankfurt's Old Town, wander for an hour, have a beer and a sausage, and return to your appropriate Terminal.
If you have the option to stay in Frankfurt on your way to another European destination, make it a day or three. Frankfurt has enough to offer, and unique German sights and flavours, without having to make a larger trip to the more well known, crowded, and expensive tourist destinations.
Apparently this is true. In the 1960s an American pilot of a commercial passenger airliner landed at Frankfurt Airport. As he was taxing his jet after a successful landing he was unsure which gate or parking area to proceed to, so he asked the control tower, "Where do I go next?"
The control tower replied, "Haven't you ever flown into Frankfurt before?"
The American pilot replied, "Yes, but that was twenty years ago, and I wasn't there to land.""