Talks between the United States and the European Union on sharing confidential airline passenger information have broken down, according to the EU.
The US had requested 34 pieces of data on each airline passenger
But officials say there will be no disruption to transatlantic flights.
After 9/11, US authorities demanded that airlines should provide personal passenger data for all inbound flights.
But the subsequent US-EU agreement was ruled illegal by the highest European court in May of this year. Saturday was the deadline for a new deal.
A European Commission spokesman said that a legal black hole could be created by the lack of agreement.
"There is no agreement. There is a legal vacuum as of midnight tonight," EU Transport Commission spokesman Jonathan Todd said on Saturday.
As a result, airlines refusing to provide passenger lists to the US may lose landing rights in the country, but those that do risk facing legal action under EU member states' data protection legislation.
But Mr Todd told BBC television that attempts to resolve the deadlock would continue.
We are confident we can move forward to a mutually acceptable agreement
US Homeland Security Secretary
"We will be discussing this at the highest political levels to see how we can take if forward. There is an imperative to sort it out sooner rather than later," he said.
However, US Homeland Security Secretary Michael Chertoff told Reuters news agency that there was "absolutely no basis" to say that discussions had broken down.
"We are confident we can move forward to a mutually acceptable agreement," he said.
He said he had been assured that European airlines would continue to provide the required passenger information and said he doubted European governments would penalise them for this.
Since 2003, US authorities have requested that airlines provide passengers' personal data to American security officials, including credit card information and telephone numbers.
A total of 34 pieces of data must be transferred to authorities within 15 minutes of a flight's departure for the US.