12. What U.S. passenger airline only operated its L-188 Lockheed Electras for cargo, not passengers?
Hawaiian Airlines (HA) Correct!
I remember seeing Hawaiian Air L-188s sitting in Denver and Los Angeles. Never saw one in Hawaii though... Makes me wonder if they were doing contract work...
I believe the bulk of the Hawaiian Electra freighters never saw Hawaii, but did regular contract work for freight forwarders and the military on the mainland. They were based in, of all places, Macon GA.