Hi,
I am currently booked for a PEK - ORD itinerary this June 15th, with a separate booking mid July for BOS - PEK. Both are economy flex fares, the one where you can upgrade with miles and change for only fare difference with no change fee.
How does it work with upgrading to J at the airport or a couple days ahead? Is it possible to pay an extra amount of money at the airport or with asia miles to upgrade to J?
Thanks