Aena, the airports authority, is currently in the process of replacing the ILS instrument landing system at Palma Son Sant Joan Airport. As a consequence of this, according to Aena terminology, the airport has been lowered from category three to category one. In practice, when there are adverse weather conditions, such as the dense fog on Wednesday, the result is that planes can't land, which is what happened on Wednesday morning.
The airports authority says that this work had been planned in advance and that it is taking a total of two months to complete. The impact on Wednesday was mainly between 7am and 10.30am. There were cancellations of flights to Palma, while some were diverted to Ibiza and other airports. For airlines, a general view was that they couldn't understand how an airport such as Palma, the third busiest in the Aena network, could have been affected in such a way.
The met agency Aemet says that the fog won't be quite as dense on Thursday as on Wednesday morning, but it is likely that there will be further problems.
Aena stresses that the airport was not closed but accepts that it was the case that flights from mainland and foreign airports were "temporarily" unable to land. Other flights were delayed, while there was a knock-on impact on departures.