Passengers on JetBlue will soon be able to use e-mail and instant messaging, thanks to a new onboard wireless network the airline will begin testing next week. Details won’t be officially announced until Tuesday, but JetBlue has outfitted one of its Airbus A320 planes — now dubbed “BetaBlue” — with an air-to-ground system featuring wireless hotspots throughout the craft, said Sebastian White, a spokesperson for the airline.