The chief executive of one of the US’s largest airlines once greeted a new “open-skies” aviation accord by saying wrily: “Great. Now we get to fly all over Singapore.”

This week’s impasse in long-running efforts to secure a more liberal agreement between the US and the 25 members of the European Union may generate a similar sense of anti-climax. The pact suffered a severe setback when the US abandoned plans to give overseas investors more influence in management of its airlines.