Haze from Indonesian forest fires has spread to the southern Philippines, disrupting air traffic and prompting warnings for residents to wear face masks, authorities said Friday.
The large southern Philippine island of Mindanao is more than 1,200 kilometres (745 miles) from the nearest fires but the haze has become a worsening problem over the past week, aviation authorities said.
Two domestic flights have been cancelled and dozens delayed at 10 airports on Mindanao since October 16, affecting thousands of passengers, Civil Aviation Authority of the Philippines spokesman Eric Apolonio said.
Apolonio said, on some occasions, pilots could not see the airstrip as they were coming into land.
"If you cannot see the runway it is very dangerous. You cannot always depend on instruments," he told AFP.
Dense haze hung like a cloud of dust over Davao, Mindanao's largest city with 1.5 million people, on Friday afternoon, plunging it under an early twilight.
Its airport, one of those affected according to Apolonio, handles 48 flights a day.
With visibility down to 1.2 kilometres at some times during the day, aircraft are forced to circle and wait above the runways for up to an hour, according to Apolonio.
Pilots can normally see up to 10 kilometres, he added.
Apolonio said the flight delays were also disrupting the busy Manila airport, with some Mindanao-bound flights being held back.
Because Manila airport is operating at its full capacity of 40 landings and take-offs per hour, any delay involving Mindanao flights disrupts the aircraft queue for the rest of the day, he added.
For nearly two months, dense haze produced by Indonesian slash-and-burn farmers have suffocated vast expanses of Southeast Asia.
This has caused rates of respiratory illnesses to soar, schools to close, and scores of flights and some international events to be cancelled.
Much of the burning is in peatlands being drained and cleared at a rapid rate to make way for agriculture.
The southern Philippines has not been badly impacted.
It may have worsened recently due to Typhoon Koppu, which hit the northern Philippines on October 18, drawing the haze towards it, state weather forecaster Victor Flores told AFP.
The haze was not so bad as to raise a medical alarm, but residents in affected areas are being advised to wear face masks, according to health department spokesman Lyndon Lee Suy.
"The content (of the smoke) is not that much but even small amounts of ash could trigger an asthma attack, or cardio-pulmonary obstructive disease," he told AFP.