In a year of low-cost travel, there soon may be even better news for the traveler.

A series of agreements recently signed or initialed by the United States pave the way for lower air fares and increased services to Belgium. Germany and Poland.

"The most liberal agreement yet" under President Carter's pro-competition international aviation policy was initialed last week by Belgium and the United States, according to James R. Atwood, deputy assistant secretary of State for transportation affairs.

Under the agreement, airlines will be freer than ever of government interference with their fares on flights between the two countries and beyond as well.

The Belgians agreed, for instance, that a U.S. airline could charge anything it wanted on flights from Brussels to other European cities unless both the Belgian and U.S. governments disapproved the fare, a situation considered very unlikely with the current U.S. policy. In order to protect its own airline's traffice, a country generally insists that it has the power to turn down fares proposed for those routes by outside carriers.

The Belgians also agreed that the fares of third country airlines on the U.S.-Belgium route could to into effect unless both governments turned them down, thus allowing third flag carriers to be price leaders.

The agreement also contains:

Expanded opportunity for charters under a provision allowing U.S. airlines to operate charters to Belgium under the more liberal U.S. charter rules, a provision that has been included in some recent agreements. But the Belgians also agreed to let the U.S. airlines operate charters out of Brussels for Belgian citizens under U.S. rules as well.

The elimination of all limitations on capacity to Belgium and to cities beyond it, and freedom of the airlines to use any kind of airplane they want coming in and going out. Agreements generally still contain restrictions on the number of seats U.S. airlines can fly into their countries as well as out, and often insist the airline use the same large plane to fly on to the next city, even if it has restricted the number of passengers the airline can carry. This provision allows the airlines the maximum amount of operating flexibility.

Complete deregulation of air cargo.

The agreement opens up Brussels completely," Atwood says.

In return, Belgium, which currently has route authority to New York and Atlanta, will get three new cities, two immediately and one to be named in six months. They have not yet named the cities but have expressed some interest in serving Washington and Chicago.

In addition, the Belgian carrier will get the authority to fly Belgian passengers on to Mesico and Canada, although it will not be able to pick up local U.S. passengers except at one point of its choosing to Mexico City.

An agreement signed a week earlier with West Germany does not embrace the "open skies" concept the U.S. proposed in September - under which the airlines of either country would be able to fly to any point in the other - but it is a far-reaching pact that substantially expands airline competition to Germany and, with the Belgian agreement, probably sets the stage for even more liberal accords with other countries.

Under the agreement, German-designated airlines - presumably Lufthansa German Airlines - are given phased-in landing rights to six additional U.S. cities. Effective immediately, they may introduce air service into Miami; San Juan, Puerto Rico; and one additional point to be selected by the German government. On April 1, 1980, Atlanta and another point chosen by the Germans will become available. On April 1, 1981, the German authorities may select a final point to be served.

Lufthansa currently has rights for Anchorage, Boston, Chicago, Los Angeles, New York and Philadelphia.

In return, the U.S. got most of what it was seeking in the new agreement:

The right to name as many U.S. airlines as it wants for U.S.-German routes.

U.S.-designated airlines will be permitted to fly from anywhere in the United States to anywhere in Germany.

The removal of all restrictions on flight capacity on U.S.-German routes.

Authority over fares for any flights originating in the United States. Although the United States had wanted authority over fares proposed by U.S. airlines for flights to and from Germany so the German government could not turn down fares proposed by U.S. carriers for traffic originating in Germany, the new provision is a great advance from the prior agreement, under which approval of both countries was needed for fares in either direction.

The right of U.S. airlines to operate charters to Germany under U.S. rules, although it did not get the more liberal charter provision in the Belgian agreement.

Letting U.S. carriers use any kind of plane on routes between German and other European cities, but the planes going out from Germany cannot exceed the seat capacity of the planes used coming in, so it is not as flexible as the Belgian agreement.

A third agreement, initialed late last week, substantially liberalized existing restrictions on U.S. air service into Poland, according to Michael Styles, director of the Office of Aviation of the State Department.

The Polish government agreed the country in which the traffic was originating would have sole jurisdiction over the scheduled and charter air fares charged from that country, and there would be no restrictions on frequencies. Each country would get the right to serve an additional point in the other's territory - a provision that means something only to Poland - but that is conditioned on a change in the Warsaw airport policy to allow the use of wide-bodied aircraft. (LOT - Polish Airlines - currently doesn't own any wide-bodied craft.)

Because a U.S. airline cannot sell tickets in Poland for Polish currency and therefore must sell tickets only through its competitor. Styles said, Poland agrees to guarantee that it will sell a certain amount of U.S. airline tickets to Polish-originating traffic. Using current traffic statistics, the sales would have amounted to about $4.5 million this year had the provision been in effect, Styles said.