The U.S. is preparing to downgrade Mexico’s air-safety rating in a potential blow to what has been one of the few strong airline markets during the pandemic.

The Federal Aviation Administration in coming days will designate Mexico as Category 2 in its International Aviation Safety Assessment Program, said two people familiar with the action who asked not to be identified because the decision hasn’t been announced.

Mexican airlines can continue to fly to the U.S., but the downgrade will prevent any expansion of flights and could limit business arrangements between carriers in the two countries. It also sends a powerful signal that could sway consumer decisions on choosing flights between the two neighbors.

FAA audits of other nations’ aviation systems don’t look at individual carriers, instead focusing on whether countries have adequate safety regulations and the resources to enforce them. The baseline is whether countries meet the standards of the United Nations’ International Civil Aviation Organization.

The FAA found 24 issues of concern in an audit of Mexico’s oversight program and only a handful have been resolved, said one of the people. The notification of the agency’s decision is imminent, the people said.

Mexico is confident the FAA won’t lower its rating after the country’s Federal Agency of Civil Aeronautics responds to the audit, said an official at the Transportation and Communications Ministry who asked not to be identified discussing the sensitive issue. The official said the FAA had identified 28 issues.

Representatives for Delta Air Lines Inc. and Grupo Aeromexico SAB had no immediate comment. Delta and Aeromexico began a joint venture in May 2017, blessed by antitrust regulators, which allows the carriers to coordinate schedules and fares on transborder flying. Atlanta-based Delta owns 49% of the Mexican airline.

Hot Market

Passenger volumes between Mexico and the U.S. this year were more than 10% higher compared to equivalent weeks in 2019 before the pandemic, according to the Airlines for America trade group. That makes it the only market that isn’t severely depressed due to Covid-19 concerns.

Most countries are rated Category 1 by the FAA; only eight other nations around the world have been downgraded, according to the agency. The FAA took the same action against Mexico in 2010 but lifted the restrictions several months later.

Among those that remain at Category 2 is Pakistan, which the FAA acted against in July following a fatal crash and revelations that hundreds of airline pilots had received fake licenses.

The FAA’s action on Mexico was earlier reported by Reuters.