It took more than four years and there are still some details to be worked out, but the United States and the European Union have finally approved an "open skies" agreement that should make trans-Atlantic air travel cheaper and more convenient.

Basically, starting next March, it would allow airlines of the EU countries to fly to any American city and allow U.S. carriers to fly to any destination in the EU's 27 countries.

The agreement would replace a restrictive web of bilateral aviation treaties. The impetus for the deal began in 2002 when a Europe-wide court began ruling the bilateral agreements illegal under EU law.

The signers have high hopes for what open skies will do for the vital trans-Atlantic market that already accounts for 60 percent of all international air travel. EU officials estimate that within five years it will add 26 million passengers to the 50 million who now fly each year, bring in $16 billion in additional revenues and add 80,000 new jobs here and in the EU.

The British were the most reluctant party to the agreement, one reason being they don't want to add to the four carriers, two British, two American, currently allowed to operate trans-Atlantic flights from busy Heathrow.

But the British, along with the rest of the EU, are eager for progress on what is to be the next stage of the agreement.

Currently foreign investment in U.S. carriers, who aren't exactly awash in fresh capital, is limited to a 25 percent stake. EU carriers would like the right to merge with, and even buy outright, U.S. airlines.

This is only good economic sense, but given American super-sensitivities to foreign ownership - the Dubai ports deal, a Chinese firm's attempt to buy Unocal, for example - that could be a tricky process.

One aspect of the next round that should not be so tricky is to allow an EU carrier to fly from one American city to another one; in effect, flying domestic routes. American flights to the EU already have won the right to fly on to other EU destinations.

It's time to offer more choices to passengers on both sides of the Atlantic.

Open skies could well be better skies.