A recent European court opinion has left US airlines urging their government take urgent action to address the risk that Ireland’s aviation regulator will cap passenger numbers at Dublin airport.

Trade group Airlines for America (A4A) says the US Department of Transportation (DOT) must “act immediately” because a European court seems likely to rule that passenger caps do not violate EU regulations.

“We urge the [DOT] to ensure that the Irish government enacts legislation and removes the passenger cap at Dublin by the end of April 2026,” says A4A in a 20 February filing with the DOT.

Aer Lingus, meanwhile, is urging the DOT to reject A4A’s request, saying the trade group has exaggerated risks posed to US carriers.

Meanwhile, Ireland’s legislation is considering a bill that would block the caps, but that measure has not yet passed.

The issue stretches back to 2007, when Dublin’s planning board capped Dublin airport to 32 million passengers annually to address congestion concerns arising from opening Terminal 2.

The airport only recently started butting up against the cap, prompting the Irish Aviation Authority to prepare to start limiting flights.

US airlines and Aer Lingus oppose the caps and filed a lawsuit seeking to block them from taking effect.

The airlines won a temporary victory in 2024 when Ireland’s High Court issued a stay prohibiting the caps pending resolution of the litigation. Then the High Court last year asked the EU Court of Justice to decide if passenger caps violate EU regulations.

The court has not issued a final decision. But on 12 February, an advocate general with the court issued an opinion saying caps would not violate regulations.

A4A views the opinion as prescient, predicting the court will ultimately issue a similar ruling. A4A fears the caps could take effect before Irish lawmakers finalise the bill outlawing the caps.

By then, A4A says, US carriers would have lost Dublin operating slots, “with no opportunity to appeal”.

A4A initially brought its concern to the DOT in January, saying caps at Dublin would violate the US-EU air transport agreement. It wants the DOT to respond by threatening to cap Irish airlines’ flights to the USA.

Aer Lingus, meanwhile, is walking a fine line. It has joined US airlines in opposing passenger caps but is fighting against A4A’s request that the DOT take action.

In a 27 February filing with the US regulator, Aer Lingus accuses A4A of “hyperbole”, saying the group is exaggerating threats.

“Retaliatory measures remain unjustified and unnecessary, and they would harm not only Aer Lingus but its valued US partners,” the Irish carrier says.

Aer Lingus adds that Ireland’s legislature will likely eventually pass the bill banning caps.