Aides to Mayor Bloomberg are floating a plan by which the city would take ownership of the World Trade Center site from the Port Authority. In return, the Port Authority would take ownership of the land under La Guardia and Kennedy Airports that now belongs to the city. Mr. Bloomberg and his aides deserve some credit for creative thinking, but they will want be careful what they wish for. They might get it. Certainly gaining control of ground zero might help City Hall fulfill its immediate objective — figuring out a plan for the site that includes less commercial office space than the Port Authority wants. But that’s a goal that is achievable without giving up so much in return.

Instead, the land swap plan would make two enormous concessions to the Port Authority, an agency already awash with cash. The authority has reserves of $1.8 billion, as our William F. Hammond Jr. reports in the adjacent columns. It is collecting hundreds of millions of dollars a year in tolls on bridges and tunnels that were already paid for decades ago. So why would the city want to give it La Guardia and Kennedy? These airports are already run by the Port Authority at a massive profit. By the Port Authority’s own accounting, the agency made $48 million on La Guardia last year and $140 million on Kennedy. And this amid a down turn in the tourism and travel industry that had airlines scrambling for federal bailouts.

Compare this to the profit thrown off by the World Trade Center site under the existing lease, by contrast, about $78 million a year. Why would any clear-eyed real estate investor trade property that yields $188 million a year for property that yields $78 million? You don’t have to be a Harvard M.B.A. like Mr. Bloomberg to realize that the airports are worth more than the trade center site. It would be the equivalent of a Monopoly board-game player trading Boardwalk and Park Place for something more akin to Baltic and Mediterranean Avenues. It turns out, however, that the airports are currently leased to the Port Authority under an arrangement that returns only a trickle of the airport profits back to the city’s taxpayers. Most of the cash gushes into those Port Authority coffers.

The city has been fighting for a better deal for some time. Under the swap plan, however, rather than continuing that fight, the city would simply surrender to the Port Authority. “We want to be in control of our own destiny,” the mayor said yesterday. In other words, at the moment the city is not in control of its own destiny, at least when it comes to the World Trade Center site. Mr. Bloomberg has been careful to couch such sentiments in civil terms. One gets the feeling that if he spoke his mind, he would say something like, “It’s a disgrace that the citizens and taxpayers of New York City are going to have to give away our valuable airports so that we can get something that we should have had to begin with — the ability to proceed with the redevelopment of Lower Manhattan without being held hostage to the revenue desires of the Port Authority.”

“And by the way,” one can imagine the mayor wanting to tell the voters, “the Port Authority — that rich agency that wants to cram all that office space onto ground zero so it can collect the rent — is basically controlled by the governors of New York and New Jersey. And, oh, by the way, did I mention that the governor of New York is up for reelection in November?”

Mr. Bloomberg, of course, needs Governor Pataki’s cooperation on too many other matters to put the case to the people this starkly. And it would be considered poor form for Mr. Bloomberg to launch this kind of attack on Mr. Pataki, who is, after all, a fellow Republican. There are no such constraints, however, on the Democrats who are running for governor. If Andrew Cuomo or H. Carl McCall is looking for an issue that will help them with New York City voters, how’s this for one: Why should the city have to give away its airports in order to get from Governor Pataki’s Port Authority something it should already have — control of its own destiny?