Platinum Aviators are not exempt from upgrade availability restrictions on domestic flights -- just like Elite and Elite 1 Aviators.

Since I have been a Platinum, I have upgraded on all but 3 of about 75 flights -- one of which was due to a cancellation.

My experience is that TWA leaves a certain number of seats as not eligible for upgrades until the day of flight -- however this is usually only 2 or 3 seats. Any remaining F seats are given out for upgrades at the airport.

My advice is to keep calling to check for availability.. if that doesn't work ask to standby for an upgrade at the airport.

Greg