Airlines must de-board any passenger before departure if they refuse to wear face mask inside an aircraft even after being warned, aviation regulator DGCA said on Wednesday.

If any passenger refuses to wear mask or follow COVID-19 protocol in a flight mid-air, the airline may bar them from flying for a certain period of time by classifying them as "unruly passenger", the Directorate General of Civil Aviation (DGCA) said in a circular.

Besides, airport operators must take help of the local police and security agencies and levy fines on people not wearing face masks in terminals, it noted.

The circular followed a Delhi High Court order of June 3 which said the "DGCA should issue separate binding directions to all staff persons deployed at the airports and in the aircraft, including flight attendants, air hostesses, captains/pilots and others, to take strict action against passengers and others who violate the masking and hygiene norms".

All such persons as are found violating the norms must be fined and persistent defaulters must be placed on the no- fly list, the court had said.

The DGCA's Wednesday circular said airlines must ensure the passengers wear masks properly on flights and they are removed from faces only "under exceptional circumstances and for permitted reasons".

If a passenger needs an extra face mask, the airline must provide it, it noted.

"The airline shall ensure that in case any passenger does not adhere to above instructions even after repeated warnings, he or she should be de-boarded, if need be, before departure," it said.

In case any passenger refuses to wear mask or violates the COVID-19 protocol even after repeated warnings in flight mid-air, he can be treated as "unruly passenger" as defined in the DGCA regulations, the circular said.

The DGCA regulations give powers to airlines to ban passengers for a certain period of time after they have been declared "unruly".

Central Industrial Security Force (CISF) and other police personnel deployed at the entrance of the airport must ensure that no one is allowed to enter the premises without wearing a mask, it said.

All airport operators must increase announcements and surveillance to ensure that passengers at terminal are wearing face masks properly and following COVID-appropriate behaviour at all times within the airport premises, it noted.

"In case any passenger does not wear mask or refuses to wear mask and follow COVID-19 protocol, he should be fined as per the respective state law where the airport is located and he may even be handed over to security agencies," it said.

Airport operators must take sanitisation measures at airports and provide hand sanitisers or dispensers at prominent places in the terminal, it noted.

"Also, airport operators shall levy fines on those violating COVID-19 protocols in accordance with state regulations with the help of local police and security agencies for violation of COVID-19 protocols," it added.

When Centre resumed scheduled domestic flights on May 25, 2020, after a two-month-long lockdown due to the COVID-19 pandemic, the DGCA had made it mandatory for passengers to wear masks and follow other COVID-19 protocol inside airport and aircraft.