President Barack Obama on Tuesday signed a bill that would protect U.S. flights from having to pay for carbon emissions credits when flying in and out of Europe. "It never made a bit of sense for European governments to tax our citizens for flying over our own airspace -- and with the passage of this law we've got the tools we need to prevent it from happening and protect American jobs," said Sen. Claire McCaskill, D-Mo., a co-author of the bill.