Germany is home to over thirty commercial passenger and cargo airports as well as a large number of smaller airfields and air strips that service business and general aviation. Of the commercial airports over two dozen can be considered “international airports”. These international airports range in size from the mega complexes in Frankfurt and Munich servicing tens of millions of passengers a year to smaller airports in medium size cities that may fly anywhere from 220 thousand passengers (Zweibrücken Airport) to over 5.2 million passengers (Hannover Langenhagen Airport). The large airports can have up to 125 different airlines serving hundreds of destinations with hundreds or of takeoffs and landings each day. Many of the medium sized airports offer flights by mainstream airlines such as Lufthansa as well as trips on low-cost and charter airlines such as RyanAir, German Wings, Air Berlin TUI and Condor. They also often offer substantial numbers of flights to cities throughout Germany and Europe. In the smaller airports much of the traffic is with low-cost airlines and charter companies. The charter carriers most often serve vacation destinations in warm climates. The former U.S. air base at Hahn, 75 miles from Frankfurt, was one of the first to offer flights from low-cost airlines and also served as a model for the conversion of former military air bases to commercial airports. There is also a very successful program to link air travel to rail travel at certain large hub cities. High-speed InterCity trains directly serve the Frankfurt, Düsseldorf, Cologne-Bonn and Stuttgart airports.