South Korea's low-cost carriers suffered an extended loss in the first quarter as the coronavirus continued to weigh on travel demand, data showed Tuesday, raising concerns over their ability to stay afloat even after the pandemic.

Budget carriers have grounded most of their flights on international routes since early 2020 as many countries placed restrictions amid virus fears, facing cutthroat competition for cheap domestic flights.

While the nation's full-service carriers have managed to make ends meet via their cargo businesses, low-cost carriers have suffered deeper losses due to a lack of larger fleets capable of delivering more freight.

All of the nation's three major LCCs -- Jeju Air Co., Jin Air Co. and T'way Air Co. -- logged operating losses in the January-March period, with their debt ratios well over 100 percent, meaning they have more debt than equity capital.

A key barometer of financial soundness, the debt ratio is calculated by dividing a company's total liabilities by its stockholders' equity.

Jeju Air, the nation's largest budget carrier by sales, posted 41.8 billion won ($36.7 million) in sales and 87.3 billion won in operating losses in the first three months of the year.

It had 137.1 billion won in equity capital versus 966.8 billion in debt, with its debt ratio coming to 705 percent, up from 439 percent a year earlier.

Jin Air, the budget carrier unit of top full-service air carrier Korean Air Lines Co., booked 43.9 billion won of revenue and 60.1 billion won of operating deficit in the January-March period.

It reported a debt-equity ratio of a whopping 1,793 percent, up from 476 percent a year earlier due to a sharp drop in its equity.

T'Way Air Co., posted 35.3 billion won of sales and 45.4 billion won of operating losses in the quarter that ended in March.

To ride out the crisis, T'way Air issued new shares worth 80 billion won in April, the first such financing among local LCCs and its second capital increase in five months.

Other LCCs are ramping up efforts to raise capital to avert potential liquidity crises, but concerns have risen over their ability to stay afloat until the air travel normalizes in the post-pandemic era.

Market watchers predicted it could take longer for international travel demand to recover to the pre-pandemic level, with the trade body ACI Europe, which represents European airports, predicting that passenger numbers won't recover until 2024. (Yonhap)