I have been looking at a ticket with the same issue. When I attempt to make a reservation on united.com and request First class, or business class does the same as this is a two class flight, I am offered an inexpensive FC fare which I assume is an instant upgrade from coach at the time of booking. The webpage shows it as First Class (A) for Cabin and when I click to get more details, it shows Fare code: HUAUPN and the rules or this fare do not seem to be very explicit in answering my questions. This is a UA operated flight (I plan to pick a time served by mainline, but I see the same for United Express flights) which I would purchase from united.com on UA ticket stock with a UA flight number.

The A3 rules for UA mileage earning specify that "booking class" A earns a minimum of 1500 miles while "booking class" H earns only 500 miles, although Y would earn 750 IIRC. Aegean does not refer to a booking code or fare class, just what they call very specifically a "booking class."

So the question is for someone to please reassure me with certainty that this ticket is indeed "booking class" A and will earn the First Class miles on A 3?