This is the unofficial website of the NSF AAPF program, run by the fellows themselves. For official information about the fellowship, please go to the NSF program announcement.
The Fly America Act regulates cases when public employees, including Fellows, are allowed to be reimbursed for travel on foreign airlines. Essentially, the act requires that you travel on a U.S.-flag carrier or on a U.S. carrier's code-shared flight to the greatest extent possible; however, Open Skies agreements with the EU, Australia, Switzerland, and Japan (detailed in the GSA page above) can mean that these restrictions are not as severe as they used to be. The current NSF policy governing the use of foreign-flagged air carriers can be found here (updated April 2015).