Blue Hawaii.(Hawaiian Airlines Inc. and Aloha Airlines Inc. battle upstart airlines)

THE TRAVEL POSTERS PORTRAY a world of blue skies, waving palm trees, tropical beaches and rolling surf--an archipelago of peace and tranquility unspoiled by the unpleasant realities of the outside world. But there is trouble in paradise as the two mainline carriers, Hawaiian Airlines and Aloha Airlines, wage a battle against an upstart from the mainland, go!, which began inter-island services last June. A fourth combatant, privately owned turboprop operator Island Air, is caught in the crossfire and recently ditched expansion plans in the face of new competitive realities.