The core of Europe's single market-a ban on tariffs, quotas, and subsidies, protected by the Schengen Agreement prohibiting border controls and competition policy-seems to be holding firm.

If there were only two airlines on every route, tacit collusion between them would probably keep prices high but not so high as if there were a single airline or an explicit price-fixing agreement.

But a single clause tucked in the 74-page deal agreement set off a series of increasingly dire events that nearly scuttled the rescue brokered and financed by the Fed.