The United States has warned it may take retaliatory action if American airlines lose access to Schiphol airport as a result of Dutch plans to cut flight numbers.

US transport secretary Sean Duffy said last weekend the Trump administration was monitoring European countries that introduce “unjustified operational restrictions” in breach of aviation agreements, and would act to defend American carriers.

“For example, we are monitoring European States to ensure that they apply the balanced approach process for noise abatement at their airports and do not implement unjustified operational restrictions,” Duffy said.

The Dutch government plans to reduce the maximum number of annual flights at Schiphol from 500,000 to 478,000 in November to limit noise pollution.

The Dutch plan could affect US airlines such as Delta Air Lines, which operates 17 daily flights at Schiphol and partners with KLM, the Parool reported. The United States is KLM’s most important intercontinental market.

Legal proceedings about the flight cuts are ongoing in the Netherlands, with KLM, Delta, TUI, and airline groups including Barin, Airlines for America and Iata seeking to block the reduction.

Former transport minister Barry Madlener (PVV) decided in May to push ahead with the reduction despite criticism from the European Commission which said the required “balanced approach” under EU rules had not been properly followed.

The cabinet argues that all conditions were met and the cut is necessary to reduce serious noise disruption for local residents by 15%.

In March 2024 a court ruled the government was acting unlawfully by failing to protect residents from excessive aircraft noise. The state has appealed against the ruling but says it must act in the meantime.

A court hearing scheduled for this week was postponed after new data showed more take-off and landing slots than expected had become available for the winter season, according to the Parool.