An annoying aspect of vacationing within the Aloha State, to visitor and resident alike, is that you can't get around by just hopping in a car, bus, or train, putting on your hiking shoes or thumbing a ride.

There are six major islands in the Hawaiian chain, and unless you're into ocean canoeing or something similarly strenuous, you have to travel from one to another by buying a plane ticket. Sadly, there are no ferry boats today.

And as the cost of fuel rose over the past few years, the prices of inter-island flights also began to climb into the financial stratosphere -- at least until recently.

Today, rather suddenly, it is so cheap to fly between Oahu, Kauai, Maui, and "the Big Island" (Hawaii) that local families are more often reunited, and tourists on a limited budget no longer must limit themselves to the sands of Waikiki on crowded Oahu. In some cases, you can fly for less than half the amount charged earlier this year. And a few fares are about equal to the rates charged back in the mid-1970s.

This all came about because the spirit of intense competition was reborn in the clear island skies less than a year ago. For years, inter-island transportation was dominated by the 170-passenger DC-9 jets operated by Hawaiian Airlines, and by the 118-seat Boeing 737s launched by Aloha Airlines. Generally speaking, whenever one airline announced a fare increase, the other soon followed suit, so that flights on either would cost the same to the penny.

Both airlines offer swift, smooth hops between the islands -- short flights to be sure, and at considerable heights. In fact the speed and altitude used by these modern jets almost precludes aerial sightseeing.

Travelers who wanted to skim the green cliffs of the north shore of Molokai or peer at the desert details inside the extinct volcano crater of Haleakala on Maui generally chose the slower and lower propeller-driven, piston-engine Cessnas of Royal Hawaiian Air Service or one of the other commuter airlines.

Fares for these puddle-jumpers were sometimes a little less, sometimes a little more than for the jets.

But last December a new, upstart airline announced that starting in March it would begin making flights between Honolulu (Oahu), and the islands of Maui and Kauai. Tickets began below $25 but later rose to $33. Either fare was quite a bargain since the regular jet fares on Hawaiian and Aloha Airlines for flights between Honolulu and those two islands were then running at $47.

Mid-Pacific Airlines jumped into the air-route game not with pure jets but with the 60-passenger Japanese-made YS-11, a fuel-efficient, two-engine "jet-prop" aircraft which flies almost as low as the piston-propeller planes, and not as fast as the jets. Many nonbusiness passengers came to the conclusion that because flights were so short anyway, it made little difference if they took 10 minutes longer reaching their destinations.

Meanwhile, Aloha Airlines and Hawaiian Airlines began to lower their fares. First there were special discount flights, but gradually time-of-day and date-of-purchase restrictions were reduced and then virtually eliminated.

Then, in mid-summer, Aloha and Hawaiian announced fares even below those charged by Mid-Pacific. The "little airline that could" responded with new low fares of $20 each way between Honolulu and Maui or Kauai on early or late flights.

Hawaiian countered by announcing a "Fly Home Free" fare, which gave a round-trip for the price of a one-way. Aloha soon announced a "Jet-Along" fare on which two persons could fly for only $2 more than the regular single fare of $35.90.

Again Mid-Pacific counterattacked, again the jet airlines counter-counterattacked, and as of this writing, the best fare between Honolulu and Maui or Kauai is Mid-Pacific's $10.95 standby fare or $14.95 confirmed-flight fare before 8 a.m. or after 11:30 p.m., and all day on weekends and holidays. Aloha and Hawaiian deals are not much higher.

Meantime, Mid-Pacific has bought more of its Japanese planes and has announced it will begin flying the 170 miles nonstop from Honolulu to Kona Airport on the Island of Hawaii Jan. 15. Its introductory fare for the longer haul will be $24.95 each way, good through March 4.

That compares favorably with the $31.50 currently offered by the two jet lines each way. And that fare, instituted in anticipation of Mid-Pacific's entry into the Honolulu-Big Island market, is just half the full $63 charged by Aloha and Hawaiian for one-way flights to Kona or Hilo as recently as September.

No one knows where it will all end, and spokesmen for the three airlines are somewhat uptight about it. Mid-Pacific has claimed the other two lines are attempting to put it out of business. Local labor leaders take a dim view of that airline's nonunion work force. Aloha has said it "won't be undersold" and has begun laying off some of its employes, and Hawaiian refuses to comment on anything concerning Mid-Pacific.

Meanwhile, the traveling public continues to be the winner in this financial dogfight and -- for the moment, anyway -- inter-island travel may be the best bargain in Hawaii.