The European Union approved an aviation deal with the United States on Thursday that opens up restricted trans-Atlantic routes to new rivals, but bowed to British concerns in delaying when the agreement takes effect. Airline stocks slipped Thursday, weighed by crude oil prices spiking by nearly $2 per barre.

Britain effectively won its demand for extra time before opening up London Heathrow, the EU’s busiest airport, to more carriers. Only four airlines – British Airways PLC, Virgin Atlantic, American Airlines and United Airlines – currently have the right to fly from Heathrow to the U.S., a lucrative route that represents around a third of all EU flights to the United States.

“If no agreement is reached in 2010, each member state may – if it wishes – notify the (European) Commission of any particular rights they would like to suspend,� said EU Transport Commissioner Jacques Barrot. “The idea behind this clause is to bring pressure to bear on the U.S. in order to conclude the second stage.�

He said he did not think these sanctions would ever be put into practice because he believed that, by 2010, both the EU and U.S. would be moving toward total liberalization for aviation.

Environmentalists called the deal a move backward in efforts to fight global warming. The European Federation for Transport and Environment said more flights could completely negate other efforts to curb climate change and cut the amount of carbon dioxide released by aviation in coming years.

Credit Suisse said U.S. carriers Continental Airlines Inc. (nyse: CAL - news - people ), Northwest Airlines (other-otc: NWACQ.PK - news - people ) Corp. and Delta Air Lines (other-otc: DALRQ.PK - news - people ) Inc. were “likely bigger winners than most believe.” Access to Heathrow would help them win major corporate travel contracts, it said.

The Amex Airline Index dropped 2.2 percent, with all 11 components declining.

the price of a barrel of oil jumped $1.73 to $61.34 on the New York Mercantile Exchange, jet fuel being one of the industry’s biggest costs.

Among the index’s biggest percentage losers were the parents of American Airlines and United Airlines, which currently have the right to fly from London’s Heathrow Airport to the U.S. The open skies deal, which received initial approval from the European Union on Thursday, would open that route to more competition

AMR Corp., parent of American Airlines, fell $1.01, or 3 percent, to $33.18 on the New York Stock Exchange. UAL Corp., United’s parent, lost $1.40, or 3.4 percent, to $40.08 on the Nasdaq Stock Market.

Continental Airlines Inc. praised the European approval of open skies and said it filed with U.S. regulators to fly new routes to Heathrow and Paris. Continental shares slipped $1.08, or 2.7 percent, to $39.42 on the NYSE.

Among other big percentage movers in the index, JetBlue Airways Corp. fell 49 cents, or 3.9 percent, to $11.71 on the Nasdaq.

The EU-U.S. accord would also encourage airline mergers because the nationality-based route limits being scrapped have complicated or thwarted alliances in Europe.

In 2003, KLM Royal Dutch Airlines NV accepted a takeover by Air France SA only after the two carriers created a temporary operating structure that safeguards the Dutch airline’s landing rights under a Dutch-U.S. aviation treaty. Worries about losing landing rights helped prevent a British Airways takeover of KLM in 2000.