The European Union's highest court has ruled an agreement to share passenger data between Europe and the United States is illegal.

The two-year-old passenger data agreement between the European Union and the United States was highly controversial from the start.  U.S. officials insist that information on passengers - such as their name, address and credit card information - is vital to thwart terrorist attacks, such as the September 11, 2001 strikes in the United States.

Another would be terrorist, British citizen Richard Reid, tried to blow up a plane he boarded a few years ago.

Hugo Brady, an analyst at the Center for European Reform in London, says security officials hoped to create profiles of passengers based on small details.

"That includes how you paid for your ticket, what kind of meal did you request, where did you ask to sit," he said.  "And U.S. border officials want to run these kinds of details through a list of indicators for suspicious behavior, like boarding an aircraft."

But civil liberties groups argue the passenger agreement violates passengers' rights to privacy.  The European Court of Justice in Luxembourg appeared to side with this argument when it ruled the deal was illegal because it did not provide adequate protection for European travelers.  The court has given the European Union and the United States until the end of September to reach another agreement.

For the moment, the decision leaves airline companies in a bind.  Washington has threatened to fine those carriers that do not provide passenger information.  Samuel Coulon, a spokesman for Air France, said his company is still studying the courts decision.

"For now, we just want to have a review of the decision and understand what was said," he said.  "There is a delay of 90 days before this would be applied."

The passenger data agreement is just part of larger efforts across the Atlantic to improve security through better data collection.  The United States and European countries are also beginning to issue special biometric passports, with chips that contain fingerprints and other information about the holder.