Thousands of teachers severely disrupted access to Mexico City's international airport, forcing some travellers to abandon cars and roll suitcases on foot during a protest against education reform.
The striking teachers descended on the capital last week from across the country, staging sit-ins at the chamber of deputies and senate that forced lawmakers to move their debates in a convention centre.
President Enrique Pena Nieto pushed through Congress changes to the constitution in December in order to put education, which was considered to be in the hands of powerful unions, under government control and require teachers to undergo mandatory appraisals.
Airport director general Alfonso Sarabia said many travellers were late for planes when they were forced to take the metro to reach the two terminals after the teachers blocked roads.
But the national security council said the airport continued to operate normally without flight delays. Some airlines offered to change tickets free of charge for people who arrived late because of the protest.
An airport official said the airport may consider diverting flights to other airports "if this situation continues for several days".
Jesus Rodriguez Almeida, the city's public security secretary, said 1,700 police officers were deployed to guard the terminals, and warned that operations there would only be interrupted "over my dead body".
Federal police said it had transported 2,500 people from a metro station to Terminal 1 and would continue the service until the blockade is lifted.
Opposition lawmakers have criticised Mexico City Mayor Miguel Angel Mancera's handling of the protests, but on Thursday he countered that his government respected the right to protest and that his priority was to prevent clashes "at all cost".