Reserve seats for both Narita Express rides (September 10 and September 17).
For September 17, book Narita Express 33 departing JR Shinjuku Station at 2:08 PM and arriving at Narita Airport Terminal 2/3 at 3:23 PM or Terminal 1 at 3:27 PM. For September 10, if immigration delays make you miss the reserved train, change your reservation at the JR EAST Travel Service Center or a reserved-seat ticket machine at the airport before boarding, subject to the ticket's change conditions.