Currently updated air fares with US airways from Zurich allows to book super cheap flights to USA starting at €319! These flights (most likely error fare) are available to Philadelphia (€319) or to New York (€358). To book such a cheap flights you have to look for the flights that are departing or arriving either during October 2013 or March 2014.
Please remember that in similar cases you should not contact booking agent nor airline before the error fare is fixed to give the opportunity to another travellers to book their flights for such a great price!
In case of interest please book via Elumbus-reisen.
Travel data samples:
19.9. – 3.10.
10. – 24.10.
25.2. – 12.3.
11. – 26.3.
18.3. – 2.4.