Planning to study abroad in Europe this summer? Wait until the 'open-skies' agreement kicks in on March 30 and you'll save a boatload on your plane ticket. Michael O'Leary, chief executive of RyanAir, the Irish no-frills carrier, has plans to start a new airline that will offer base fares from US cities to locations in the UK as low as 10 Euros, or about $16.

On March 30, the so-called open-skies agreement goes into effect, allowing airlines based in the United States and Europe to fly across the Atlantic between any two airports in each region. Before the pact, trans-Atlantic flights were governed by separate agreements between the United States and individual European nations. The pacts required airlines to take off or land in their native countries, and limited which airlines could serve certain airports. For example, British Airways flights bound for the United States had to originate in Britain. And only two United States carriers were permitted to land at Heathrow Airport, near London: American and United.

When the open-skies agreement kicks in next week, those restrictions will be lifted, essentially letting the open market dictate all trans-Atlantic routes between the United States and Europe. For instance, Continental, Delta and Northwest will be able to serve Heathrow for the first time. This year, San Francisco, Orlando and Washington all received their first scheduled nonstop flights to Dublin on Aer Lingus under a related transitionary arrangement. And Michael O'Leary, chief executive of Ryanair, the Irish no-frills carrier, has said he plans to start a new airline that will fly from secondary European markets like Liverpool or Birmingham to a half-dozen American cities like Baltimore or Providence, R.I., for a base fare as low as 10 euros, or about $16 at $1.59 to the euro.