Some background on nonstop Hilo service...
Hilo was to be developed as the "second gateway" to Hawaii in the 1970s. At that time, Honolulu International Airport was under major expansion, and the 'Reef Runway' had yet to be built. Government and tourism officials thought another transpacific airport would be needed to handle the increased traffic.
In 1965-1966 Hilo lengthened its east-west runway to handle heavy jets like the 707 and DC8, and in 1969 built a temporary 'overseas' terminal adjacent to the existing building. To get the transpacific gateway off the ground, most of the routes awarded in the 1969 Transpacific Route Case included stops in Hilo or weekend nonstops.
Consequently, in the late 1960s and early 1970s Hilo was served by United, Pan Am, Northwest, Continental, Western and even Braniff for awhile. United had nonstops from SFO and LAX (as well as from ORD for a time), Northwest served Hilo from PDX and SEA, Continental from SEA and Western from LAX. All of these airlines brought in widebody DC10 and 747 aircraft after 1970.
Hilo began planning a new terminal complex to serve all of the larger jetliners, which had overwhelmed the modest terminal. The new (and current) building opened in 1976 and was the second airport in Hawaii to have jetbridges.
Most of the resorts were in Kona, though, and in the 1980s KOA began to siphon away some of the nonstop flights. Northwest, Western and Continental pulled out of the Neighbor Island market altogether. United opened up a Kona station in 1983-1984, and pulled out of Hilo completely in 1986.
Now Kona has an 11,000 foot jet runway and Hilo has a half-empty terminal. Many nonstop flights also moved to Kahului (OGG) on Maui, which can really be viewed as the state's second transpacific gateway. If only they could that runway extended...