The viability of Trinity Airways and Air Premia’s long-haul businesses remains in doubt, as both budget carriers struggle to build stable profit structures to keep their expanded operations afloat, industry officials said Thursday. The two airlines had been widely seen as major beneficiaries of remedies imposed by competition authorities to address concerns stemming from Korean Air’s acquisition of Asiana Airlines. The measures required Korean Air and Asiana to make room for rival carriers on routes where regulators are concerned the merger could reduce competition. Under these measures, Trinity Airways, formerly T’way Air, took over four European routes, flying from Incheon to Paris, Rome, Barcelona and Frankfurt. Air Premia was also selected to operate an Incheon-Honolulu route under measures aimed at preserving competition following the merger. The expansion has given the low-cost carriers (LCCs) access to major international markets, but it has also exposed them to a heavier cost structure than traditional budget airlines. Long-haul operations require wide-body aircraft, higher