The lines are drawn in what observers expect to be a protracted fight between the Massachusetts Port Authority and most aviation user groups.

The focus of the upcoming legal battle is Massport's Program for Airport Capacity Efficiency, adopted for Boston's Logan International Airport at an emotional meeting in Boston March 16.Pilot and other user groups, and now the Transportation Department, concede that other airport proprietors view the plan as a model approach to controlling access.

This thing could spread like wildfire and render interstate flight a nightmare of conflicting local rules, said Jonathan Howe, president of the National Business Aircraft Association.

Before the echoes of the session died, aviation user groups started moving their fight against Massport from the authority's doorstep and into legal venues.

By week's end, user groups opposing the plan had raced to the court house to file discrimination suits against Massport.

At the same time, the business aircraft association filed a formal complaint against the airport authority with the Federal Aviation Administration .

The business aircraft association filed its so-called Part 13 complaint the day Massport adopted Phase I of the plan, which raises landing fees for private aircraft up to 260 percent while lowering the average fee charged to large commercial jets.

The two-count complaint alleges that Massport violated obligations made when accepting federal funds under the Airport and Airway Improvement Act.

The first claim centers on violation of the fair and reasonable terms for airport access rules.

The second claim alleges that Massport must operate under access rules that do not impose unjust discrimination on any particular type of user.

It looks like a repeat of 1983, when most of the industry went to war against the White Plains, New York, airport, said an FAA official who asked to remain anonymous.

This time appears no better for the protagonists, but just as bloody for everybody concerned, the official added.

Aviation user groups and the Federal Aviation Administration went into court against the White Plains airport management when it attempted to prohibit certain types of operations.

After spending millions on legal fees, the opposing parties reached an accommodation closer to the status quo of the day than originally envisioned by the airport proprietors.

The business aircraft association and Aircraft Owners and Pilots Association both plan federal court challenges to the Massport plan.

Observers say the weaknesses in the authority's case stem from claims that aren't supported by available information.

They are telling the Boston community that driving out general aviation will reduce congestion and noise, noted Edward Stimpson, president of the General Aviation manufacturers association, another group opposing the plan.

What they haven't said is that replacing small aircraft with large jets will only increase noise levels, Mr. Stimpson added.

Because of the Part 13 complaint, named because it is a process outlined in Federal Air Regulation Part 13, the FAA has no choice but to enter the fray.

Previously, Transportation Department Secretary James Burnley took a wait- and-see position over the months-old controversy.

Last week, however, Mr. Burnley gave hints that his position is changing.

In fact, now that Massport has acted, Mr. Burnley can rightly claim he allowed the local community to decide its own action, noted a DOT official.

Mr. Burnley can now observe that the PACE plan flies in the face of the Interstate Commerce Clause of the U.S. Constitution, noted Mr. Stimpson.

Airport groups decry federal involvement, saying that airport managements have the right to decide their own policies.

The only weakness in that view is that those policies must be consistent with national policies and laws, noted an FAA official.

And if the plan indeed serves as a model approach for other airport proprietors, pilot groups and federal officials say that the outcome of the pending challenges will also act equally as a model of what not to do.

When we stopped Santa Monica, Calif., from banning all turbine aircraft, we never again saw that move attempted, noted an owners and pilots association official.

We all hope defeating PACE will serve aviation in the same way.