A group of passengers could face hefty fines after delaying a Vueling flight in Barcelona out of sympathy with a Senegalese migrant on board.
The Senegalese man, in handcuffs, was eventually deported to Dakar on the flight. The jet took off after police had come on board to stop the protest.
The 11 protesters could be fined up to €225,000 (£197,000; $258,000) each for endangering flight safety.
The protest delayed both that flight and the return flight from Dakar.
Spanish media report that the Barcelona-Dakar flight was delayed by two-and-a-half hours at El Prat airport on Saturday, after all the passengers had been ordered off the plane.
When they boarded again, 11 passengers – identified by police as protesters – were not allowed through.
A Spanish journalist, Anna Palou, tweeted a video clip showing the protest on the budget airline jet.
The clip showed several passengers blocking the aisle and bore the message in Catalan: "We have succeeded! Flight of deportation stopped. Now the authorities are coming to take the person away! Solidarity is our best weapon!"
The BBC has approached Vueling for comment on the incident.
Witnesses quoted by Spanish media said the sympathy protest started on the plane when the Senegalese man, escorted by two border guards, complained loudly about being deported.
Lacking any work or residence permit, he had been refused entry to Spain, the Efe news agency reported.
The delay meant that the return flight from Dakar had to be postponed to Sunday, forcing Vueling to pay for the overnight accommodation of 176 passengers.
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The incident prompted anti-deportation activists to rally at Seville airport on Sunday. The activists, from the group Caravana Abriendo Fronteras (Open Borders Caravan), staged a noisy protest in the airport terminal.
The numbers of migrants and refugees arriving in Spain from Africa this year have increased compared with the same period (January-July) last year.
The International Organization for Migration (IOM) says 6,973 had arrived in Spain by sea as of 11 July, compared with 2,476 in the first half of last year.
However, far more took the Central Mediterranean route to Italy.