(Bloomberg) -- An airline group and a pilots’ association are ringing the alarms on Mexico City’s airspace, saying they’ve seen a worrying increase in ground proximity warning events since the space was redesigned last year. 

Benito Juarez International Airport recorded at least 17 such warnings since April 2021 as part of an alert system that notifies when planes are in danger of flying into the ground or an obstacle, according to a letter signed by the International Air Transport Association and sent to Mexico’s aviation authorities. 

“We want to express our concern, shared by our international members, over the significant increase in ground proximity warning events in the terminal area of Mexico City’s International Airport,” reads the letter, dated May 3, from IATA Americas’ Regional Director of Operations, Safety & Security. The letter was addressed to the head of the Navigation Services agency in Mexico, Seneam. 

The agency said it hadn’t received anything from IATA. The group confirmed it had sent the letter to the agency. 

Additionally, the International Federation of Air Line Pilot’s Association said there were several incidents in the past month in which aircraft arrived with low fuel due to unplanned holding and diversions for excessive delays. The association said this was due to the opening of the Felipe Angeles airport in March, which required a controversial redesign of the capital’s airspace. Air traffic control has “apparently received little training and support as to how to operate this new configuration,” according to a statement. 

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The Felipe Angeles airport is located about 50 kilometers (31 miles) north of the capital’s center and is meant to relieve saturation at the Benito Juarez airport. But experts have said the redesign is flawed and that it ignores the metropolis’s unique geography -- Mexico’s capital is mostly ringed by mountains and its altitude is more than 7,000 feet (2,100 meters), making landing aircraft more difficult.  

In its letter, IATA said the changes have led to “a very worrying situation” that has triggered the alerts and has led operators to undertake urgent mitigating actions. The organization, which represents the world’s airlines and was founded in 1945, cited data that showed the main contributing factor to the events was the lack of adherence to communication protocols between flight crews and air traffic controllers on the ground. 

Mexico’s aviation-safety ranking was downgraded by the U.S. Federal Aviation Administration in May 2021, prohibiting an expansion of flights from the nation’s carriers to the U.S. 

An improvement in the rating could still be some months away, and issues with the airspace “won’t help the process,” IATA said in the letter, which was first reported by business columnist Dario Celis. The organization declined to comment further. 

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