The main access route to this capital's international airport was blocked Friday by some 5,000 teachers angry about a sweeping overhaul of Mexico's schools.
Police were reported to be negotiating with members of the militant CNTE teachers union to dissuade the protesters from getting any closer to the airport.
Though the protest is hampering access to the terminals, flight operations have not been affected, airport director Alfonso Sarabia told Radio Formula.
Describing Mexico City International as a "strategic installation," he said authorities responded to his request for help by deploying 1,700 federal and municipal police to guard the terminals.
The capital airport handles some 970 flights a day.
"Many passengers are arriving late," Sarabia said, adding that some travelers are reaching the terminals by hitching rides aboard airport vehicles and armored cars.
"It's a pretty major disruption," the airport boss said.
Other CNTE contingents remained entrenched Friday around the seats of Mexico's Senate and lower house.
The teachers' presence forced lawmakers to decamp to a nearby convention center to conclude this week's special legislative session.
The agenda for the special session included bills to implement the educational overhaul promulgated in February by President Enrique Peña Nieto, but lawmakers decided earlier this week to delay consideration of those measures pending talks with the disgruntled teachers.
The centerpiece of the school plan is a system for teacher evaluation that many educators see as a threat to their jobs. EFE