The Civil Aviation Authority has asked all major Pakistani airlines to strictly ensure compliance with a ban on smoking on board aircraft, saying "rampant" violations of the rule by cockpit crews is a safety hazard, it emerged on Friday.

In a communiqué sent to domestic airlines, CAA Flight Standards Director Capt Arif Majeed reminded operators that smoking by the crew and passengers both is prohibited on board an airplane when it is airborne or on the ground.

"[However], despite repeated reminders by PCAA on the subject, smoking on board aeroplanes by crew is still rampant," reads the letter, dated March 7.

"Smoking on board an aircraft is a threat to its safety and an offence under state law," it said, recalling that the Prohibition of Smoking and Protection of Non-Smokers Health Ordinance 2002 forbids smoking at all public places, institutions and public service vehicles.

Majeed stated in the letter that safety assessment inspections carried out abroad on Pakistani aircraft in the past have often reported evidence of smoking in the cockpit.

"This flagrant violation [of the rule] besides portraying [a] bad image of Pakistani pilots as principal violators is also a major reason for negative marking [in safety assessments] of Pakistan-registered aircraft," he said.

The negative marking has an adverse impact on the cumulative safety assessment of Pakistani airplanes.

Directing airlines to immediately implement the smoking ban, CAA has asked them to include the rule in the operations manual along with details of punitive actions.

In addition to the pilots, passengers and cabin crews are also barred from smoking in the cockpit, the letter stated. If it emerges and is proven that someone from the crew has smoked or permitted smoking, the licences of all crew members present in the cockpit will be suspended for three months.

The licence of the crew member found violating the rule on board for the second time will also be revoked, the letter stated.