If you own an aircraft that was registered in the month of April of any year, your aircraft must be re-registered by June 30, 2011. Since the window for online registration has closed, if you haven’t done so already, you will need to submit your re-registration application to the FAA by mail. You should submit your re-registration application as soon as possible since you won’t be able to operate your aircraft legally after June 30 until you receive your new registration certificate.
For May-issued certificates, aircraft owners may submit re-registration applications now through July 31, 2011. After July 31, those aircraft may not be operated legally until the owner receives the new registration certificate. You can re-register May-issued certificates online here by entering the aircraft’s N-number and re-registration code to begin the process, or you may submit a written re-registration application to the FAA via mail.
For a discussion of the FAA’s re-registration requirements, please read my article Understanding The FAA’s New Aircraft Re-Registration And Renewal Requirements.