The very low visibility conditions observed this morning at Lisbon airport demanded greater spacing of aircraft in airspace, creating operational constraints and delays in flights, the official source of ANA - Aeroportos de Portugal told Lusa.

However, he added, "the positive improvement in the weather situation" will allow "the gradual recovery of normality in operations.

TAP also warned, on its Facebook social network page, that delays at Lisbon and Porto airports "due to the heavy fog," could exist throughout the day, adding that some flights could be "diverted to other airports in the country.