Despite soaring through the Senate Commerce Committee, a bill that would bar U.S. participation in an E.U. airline emissions trading program has been stalled on the runway.

Bill sponsor Sen. John Thune (R-S.D.) said there was possibly a hold on the bill, although he could not say which senator had tried to slow it. But he said that opposition to the bill meant people were "playing shenanigans on the floor" and placed the blame on "environmental extremist groups probably [putting] pressure on a few members."

And Commerce Chairman Jay Rockefeller (D-W.Va.) said it was unlikely that the bill would see a vote before a scheduled recess at the end of next week.

"It really depends what the atmosphere of the situation is," Rockefeller said, adding that he had spoken to leaders about moving the bill but that "they're jammed."

It is a surprising result for a bill that swept through a committee hearing in July by voice vote and had Thune optimistic that it could pass the full Senate by unanimous consent (E&E Daily, Aug. 1). A companion bill cleared the House by voice vote last fall.

The bill would block American air carriers from paying into the E.U. program. The program, which took effect this year, requires airlines to pay for or reduce greenhouse gas emissions on flights to and from Europe, including segments in foreign airspace.

Thune's bill made modifications to please environmentally minded Democrats like Sens. John Kerry of Massachusetts and Barbara Boxer of California, adding language that would instruct U.S. officials to engage in international negotiations on a new emissions-reduction system and require a public hearing before imposing a prohibition on participation in the system.

Thune and co-sponsor Sen. Claire McCaskill (D-Mo.) also circulated a "Dear Colleague" letter urging fellow senators to "come forward and work with us in resolving specific concerns," although Thune said Monday he was not sure what tweaks could be made to appease the environmental community.

Although there has been broad political opposition to the E.U. program, which critics say is imposing unfair fees on international airlines and was implemented before an international agreement was able to be reached, some environmental groups have said the United States should participate. Before Thune's bill had a hearing, the World Wildlife Fund called it "misinformed and misguided."