I'm booked on UA Saver award on TG BKK-BRU in J. They are currently using the leased Jet Airways 777-300ER with F seats. Their plans is to change to their own brand new 777-300ER where J is the highest cabin. There is no definitive date for the equipment change. Saver F is available so i'm thinking about paying the extra 10K miles. What happens if the swap occurs prior to my flight? Do i get downgraded back to J where I request a refund of the miles difference? What if J saver award space is no longer available, do i get put in coach?