Nowadays Guam is incorporated territory of US in the western Pacific Ocean, your visa requirements should be possible to check here (but it seems that the visit should be free of visa requirement for most of the EU countries). Promotional tariff of China Airlines allows to purchase such a flights in travel period from 1st of September 2014 onward. We have managed to find the cheapest flights to Guam mainly within November 2014 till March 2015.
If interested in this China Airlines promotional offer please refer to below booking samples. You may also decide to book stop-over in Taipei for additional cost. In any case you would have to accept longer layover in Taiwan giving you an option to experience another culture and explore another city during your trip.
Booking samples
Frankfurt - Guam for €749
Frankfurt - Taipei - Guam - Frankfurt for €837
Alternative - if you are looking for some exotic destination in this are you may also consider roundtrip flights to amazing Palau again with China Airlines. We have posted this deal lately and it is still valid. Please follow this link to book roundtrip flights from Germany to Koror from €714.
Booking sample of cheap flights to Guam from Germany for €749 here. In this case you would be departing from Frankfurt to Guam on 28th of November. Your return flight from Marianna Islands back to Germany would take place on 14th of December 2014
