In Mallorca, the police took 12 of 24 passengers into custody until Saturday, who had used a stopover of their Moroccan passenger plane to disembark the previous evening.
21 had run onto the runway and climbed over the fence around the airport in the dark.
A passenger hit a Spanish police officer on the plane and was arrested, reported the "Mallorca Zeitung".
Another passenger, who allegedly suffered a diabetes shock during the flight of the plane from Casablanca to Istanbul and thus triggered the stopover in Mallorca, was arrested after he was found to be healthy in the hospital, the authorities said. His companion had left the hospital.
The authorities did not rule out that it could have been a planned action by a group of passengers who had intentionally brought about the forced landing in order to come to Spain illegally.
So far, there is no tangible evidence of this, said Aina Calvo from the central government delegation to the Balearic Islands.
As far as she knows, there has never been an incident like this in Spain and that is why the authorities are very careful in assessing the situation and investigating in all directions, said Calvo.
Every year thousands of people risk their lives to get to Spain in small boats from North Africa across the Mediterranean Sea.
Procedure for endangering air traffic
Son Sant Juan Airport had to stop all take-offs and landings for more than three hours on Friday evening because of the people on the tarmac. Before flight operations could be resumed around 11.30 p.m., 27 approaching aircraft had to be diverted to other airports such as Ibiza, Barcelona or Valencia, and 20 take-offs were delayed by hours. At least two flights from Germany were also affected, one of which was redirected to Valencia and the other to Ibiza, as the "Mallorca Zeitung" reported.
The passengers who got off the plane would now be treated like migrants who had arrived by boats from North Africa, the police told the German press agency. These are registered and taken to an initial reception center, later they are taken to mainland Spain. Then a procedure for repatriation to the country of origin is initiated, which can be stopped by applying for asylum or granting protection as a refugee.
However, proceedings will also be initiated against them for endangering air traffic.
A police spokesman said that only the supposedly sick person would have to face criminal proceedings on suspicion of favoring illegal entry and violating the Aliens Act.
The affected Moroccan machine was able to fly to Turkey early Saturday morning.