Looking for some advice. Travelling to the States (Miami) via BA next March. After a short stay /cruise, it’s our Intention to fly from Miami to JFK. When looking at the MIA - JFK AA flights, I’m seeing basic economy, Main and Main plus. As a one world Sapphire / BA silver, what did I need to book here to guarantee luggage, seat selection and lounge access etc ? Any advice would be appreciated.