Originally Posted by jrl767

20. Per the 1976 OAG, all but five of the three letter airport codes that begin with Y belong to Canadian airports. Each of the five US airports are served by a single airline and – with two exceptions – a single aircraft type. Identify each of these airports along with the relevant airlines and aircraft that serve them.

YAK (Yakutat AK) - Alaska, 737 (Per my schedules, this was operated with a 727-100)
YKM (Yakima WA) - Hughes AirWest, DC9 and Cascade Airways, Beech 99
YNG (Youngstown OH) - United, 737 and 727
YNK (Yankton SD) - North Central, Convair 580
YUM (Yuma AZ) - Hughes AirWest, F-27

21. Hours spent pouring over the parched pages of my OAG in the dead of night have revealed three airlines in the state of Florida that still operate Douglas DC3s. Can you identify them all?
I certainly hope that the pages were in plastic sheet protectors so that any stray water didn't ruin them for future poring
Provincetown-Boston, Florida Airlines, and Air Sunshine

Correct on all counts, J! I'm surprised you got Yankton, ND. Not many people aside from Lyle Alzado might have known that one! Well done!