The deadline for a transatlantic deal to slash government subsidies to rivals Airbus and Boeing expired Monday.
The European Union and United States accuse each other of unfairly boosting their aircraft industries with state subsidies.
Last January, Washington and Brussels sought to avoid a costly legal dispute through the World Trade Organization and gave themselves 90 days to reach an agreement on their own. That three-month negotiation period ended April 11.
The missed deadline allows the EU and U.S. to resume subsidies and WTO litigation at any time.
However, a European Union spokeswoman suggested there is still time to reach an accord.
Meanwhile, Airbus is waiting for government loans to launch its latest model, the A350, a direct competitor to Boeing's 787 Dreamliner. The United States has said it will go back to the WTO if Airbus asks for new subsidies.
Some information for this report provided by AP and Reuters.