Tourist Visa – 90 days
As long as you already have a pilot license and only wish to rent an airplane or take a currency check this is the easiest visa to enter the country. For all European countries it is done by filling out a form on the airplane flying over. This together with documentation that you will leave the country within 90 days (ex. your return ticket) gets you in. You cannot undergo flight training or obtain a pilot license or rating on a tourist visa. And after September 11th 2001 the FAA now forwards your information to the INS (Immigration and Naturalization Services) to makes sure you are legal before issuing a license.
http://www.aviationcareerguide.com/student_visas.asp
BTW, if you have received an INS form explaining to come and study under a B2 visa...it is not longer valid, because the INS(the Office) does not exist anymore!!!!