If you like to come here by plane, you need to book your flight to FRANKFURT AIRPORT (FRA). The city is called: Frankfurt am Main. It is the biggest airport in Germany and you can reach GIESSEN easily by train.
In most cases you will have the opportunity to book direct flights. We recommend these flights as they are often on same price-level as step-over-flights and quite more comfortable.
Preferred credit-cards in Germany are MASTER CARD and VISA - only 50% of shops and hotels accept AMERICAN EXPRESS. Please be aware that in Germany people usually pay in cash for amounts below 30€.