With several countries banning flights from Mexico to avoid the spread of a new influenza strain, and a number of major airlines reducing capacity to the country amid low passenger demand, Mexican airports are starting to feel the effects.

State-run airport operator Aeropuertos y Servicios Auxiliares, or ASA, said Tuesday that airlines canceled 120 flights at its airports between April 23 and May 4 amid the influenza outbreak.

Armando Alcantara, an ASA spokesman, said the canceled flights represented between 15% and 20% of ASA's total operations during the period. He noted ASA's airports are small and of regional importance, serving very few international flights.

Total traffic during the period was 44,000 passengers, ASA said.

The Mexico City airport, which is state-run but independent from ASA, saw 53 flights canceled Tuesday, of a daily average of around 900, a spokesman said.

Mexico's three privately owned airport operators - Grupo Aeroportuario del Pacifico (GAP), Grupo Aeroportuario del Sureste (ASR), and Grupo Aeroportuario del Centro Norte (OMAB), expect an impact but haven't reported numbers.

The outbreak of the H1N1 influenza virus, which has been blamed in 26 deaths so far out of 866 confirmed cases, has discouraged travel to Mexico at a time when airports were already seeing a decline in traffic because of the economic crisis. The drop in demand has led some airlines to respond.

Continental Airlines (CAL), which has the most flights to Mexico of any foreign carrier, decided last Friday to halve its seating capacity to Mexico. A number of other airlines, including U.S. Airways (LCC), United Airlines (UAUA), Air Canada (AIDIF), and WestJet Airlines (WJA.T), have also said they will temporarily reduce flights to Mexico due to low demand.

American Airlines (AMR) said Tuesday that it, along with affiliate American Eagle, will trim the number of flights on high-frequency Mexico routes from May 8 through June 10 due to weak demand. Total daily flights will be cut to 31 round trips from 42 round trips.

Tourism Minister Rodolfo Elizondo has said he expects international tourism to virtually disappear amid the influenza threat.

That's particularly bad news for Grupo Aeroportuario del Sureste, known as Asur, as the company depends on international travelers for around two-thirds of its total passenger traffic.

Four countries - Argentina, Cuba, Peru and Ecuador - have suspended flights from Mexico in an attempt to keep out the new influenza strain, which is thought to have originated in Mexico.

Other countries, including Canada and the U.S., have advised their citizens to avoid non-essential travel to Mexico.

The Communications and Transport Ministry has kept all telecommunications and transportation systems within the country operating normally.

-By Paul Kiernan, Dow Jones Newswires; (5255)5001-5726, paul.kiernan@dowjones.com