Some interesting background on the decision to cancel the flights from Paris to LAX. There seems to have been some disagreement between US and French authorities over how to handle the information.
According to this report from the BBC, Department of Homeland Security officials were pissed that the French had handled the matter so publicly, thus losing a chance to possibly arrest the folks about whom suspicion had been raised.
Meanwhile the DC correspondent of a major French media outlet tells me that French authorities looked at the list of names provided by the Americans and eventually concluded on their own that the people in question had no ties to terrorism.
Finally, this report says that a spokesman for the French Prime Minister "said the United States had threatened to refuse the planes permission to land if they did take off," which again suggests a lack of a completely harmonious interaction.
Needless to say, I don't know which of these stories are true or what's behind them. In real-time, counter-terrorism has its own equivalent of the fog of war. So even the players themselves may not know all the details. And add to this the distinct possibility that reports we hear may include disinformation intended to conceal from terrorists what law enforcement authorities do or don't know.
But, assuming nothing terrible ends up happening, I'll be very curious to find out more about just how this was all handled. Because few things are more important than effective liaison and coordination between ours and our allies intelligence services. And if the choppy political waters are getting in the way, on either side, that's a big problem.