South Korea’s government said Thursday that it had set tougher safety guidelines for budget airlines after a series of recent mishaps raised alarm bells about the rapidly growing transportation sector.

The measures, which include stiff penalties for noncompliance, are designed to fundamentally overhaul the way low cost carriers run their operations, the Ministry of Land, Infrastructure and Transport said. 

Under the plan, each carrier will be required to have six sets of pilots for each of its planes, as well as 12 qualified mechanics to service each jet.

These companies will also be required to have a fully operational plane and crew in reserve in case mechanical problems arise on a scheduled flight.

The ministry said that while the new rules cannot be made into law, failure to comply can lead to flight suspensions, cuts in routes carriers can service, and disadvantage in getting new slots for future routes. In case of serious noncompliance, the ministry can even revoke a carrier’s air operator certificate.

At present, each local budget airline has 5.5-5.9 sets of flight crew for each plane, and 9-11 maintenance personnel, with most having no planes in reserve.

The ministry actions follow probes into two incidents involving jets from Jeju Air Co. and Jin Air Co., the two largest budget carriers in the country.

A Jeju Air jet with 150 passengers had to lower altitude rapidly because the pilot failed to turn on the cabin air supply switch after takeoff from Gimpo International Airport on Dec. 23. A Jin Air plane with 160 people on board returned to Cebu in the Philippines on Jan. 3 of this year, after an “explosion” was heard near one of the cabin doors.

South Korea currently has five budget airlines, with another getting ready to start services in the first half of this year. It also has two smaller operators that will fly jets able to carry some 50 passengers between regional cities later on in the year.

Official data showed air passenger traffic rose 9.8 percent annually in 2015, with the upward trend being bolstered by more routes being offered by the country’s no-frills airlines, that already make up a major chunk of the domestic routes.

These carriers have also made significant headways in capturing market share on international routes to destinations in Asia from their full-service rivals like Korean Air and Asiana Airlines thanks to their ticket price advantage.

Besides safety measures, the ministry said it is in the process of determining why LCCs failed to properly notify stranded passengers on boarding procedures after runway operations resumed at Jeju International Airport on Monday. The airport on the resort island was closed for nearly two days after a sudden snow storm.

Budget carriers drew flak for handing out queue tickets to people, forcing many to wait at the airport overnight.

Initial probes found that due to the lack of infrastructure, LCC did not have an automatic notification system in place inform passengers on delays and when they will be able to board next available flight.

Jeju Air apologized for the incident and said it was working on a way to solve the problem. (Yonhap)