Who does not want? It has not been allowed by airlines to have electronic products and gadgetry that would interfere with their navigational system, but the main reason was security against terrorists communicating while up high through the world wide web, having Internet access while on the sky. It had been banned since the September attack. But now, if you want free in-air access to Internet, fly with Jetblue heading from San Francisco to New York on JetBlue Airways next week, so you may get a chance to join testing in-flight e-mail and instant-messaging service. But because of bandwidth constraints, general web access and e-mail attachments won’t be permitted. Service will be accessible only to travelers using two BlackBerry models, the 8820 and 8320, and to laptop users with Yahoo e-mail and Yahoo instant messaging. The test will be on Tuesday on Flight 641 from JFK International Airport to San Francisco International. The return flight, Flight 644, leaves San Francisco at 12:25 p.m.