The Civil Aviation Authority of Vietnam said Monday that a 36-year-old man from the northern Hai Phong City has been banned from domestic and international flights for nine months.

Despite several reminders and warnings, he had refused to pay fine of VND4 million ($172) after being caught smoking in the toilet on a VietJet flight from Ho Chi Minh City to Hanoi, which took around two hours.

Another male passenger also received a nine-month flight ban starting June 20 after he failed to pay a penalty for smoking on a shorter flight with Bamboo Airways from Dak Lak in the Central Highlands to Hanoi.

Passengers are always reminded that smoking is not allowed on flights, but some still try to sneak a puff in toilets, where clear no-smoking signs are posted.

Last year, aviation authorities fined a teenage girl VND2 million ($88) for smoking on a domestic flight despite repeated warnings from the crew.

Vietnam has a high number of smokers at 15.6 million; and smoking is one of many violations that have been reported recently in the country's aviation industry. The country introduced a record 40 flight bans in 2017 for passengers who smoke, fight or steal on flights.