By Kylie Madry

MEXICO CITY Mexico said on Thursday that tariffs paid by non-government airport operators to authorities would nearly double as part of an industry reform that could rake in an extra $140 million a year.

The newly announced tariff rate of 9% of gross revenue compares to the previous 5%.

Publicly-listed Mexican airport operators OMA, GAP and ASUR collectively reported about $3.5 billion in revenue last year, meaning the new rate could lead to about a $140 million increase in costs, based on Reuters calculations.

The groups' shares fell on Thursday after the new terms were announced, with GAP and ASUR slipping about 2%, and OMA down 0.2%.

Their shares had their worst day ever on Oct. 5 on news that the first tariff changes in two decades were being tabled, though details of the new terms were not specified at the time.

OMA operates more than a dozen airports in Mexico, the largest being in the northern industrial hub of Monterrey, with GAP operating 12 including in Guadalajara and ASUR controlling nine, including in tourist hub Cancun.

Mexico City International Airport, the country's largest, is now under the control of the Mexican navy and is not subject to the higher tariffs.

OMA and GAP said the higher tariffs would become valid immediately, though GAP stipulated that, in its case, they would take effect from Jan. 1, 2025 due to a prior agreement already in place.

ASUR said it was evaluating the impact of the policy.

A spokesperson for the transportation ministry declined to comment when asked to clarify the impact of the higher tariffs.

The government insisted the adjustments would not negatively impact the groups' financial health, though analysts and opposition politicians argued the groups' bottom lines would likely take a hit.

The announcement came a day after Mexico's lower house passed a reform including the hike, as well as a measure to create two funds to funnel tax revenues to airport bodies controlled by Mexico's armed forces.

President Andres Manuel Lopez Obrador has criticized private airport operators and airlines, and has increasingly tasked the military with what have traditionally been civilian aviation duties.

Lopez Obrador has touted lower costs at military-run airports and said that a to-be-launched military-run airline, Mexicana, will offer lower fares than other commercial carriers.

(Reporting by Kylie Madry, Raul Cortes and Isabel Woodford; Additional reporting by Aida Palaez-Fernandez; Editing by Stephen Eisenhammer, Alistair Bell and Jamie Freed)