AT LONG LAST, the authority that runs the D.C. area’s two major airports and which is building Metro’s Silver Line extension to Dulles, has begun to clean up its act.

The Washington Metropolitan Airports Authority has severed sweetheart contracts with former members of its board. It has adopted guidelines that should halt the worst abuses by spendthrift, globe-trotting, politically tone-deaf members. Despite their sniping, the authority appears poised to curb nepotistic practices that have made summer internships at the authority an employment program for the well connected.

Unfortunately, the steps so far are half measures that will not extinguish the firestorm of criticism as long as the worst perpetrator of abuse remains on the board: Dennis L. Martire.

Mr. Martire, a labor official, was named to the board in 2009. In two years, he racked up more than $38,000 in travel expenses attending conferences — much more than any other member. Some of his trips were blatant boondoggles, including one nine-day extravaganza to attend a 36-hour conference on the Italian island of Sardinia. For that Mr. Martire billed (or rather, bilked) the authority $10,586 — despite the fact that the conference had nothing to do with U.S. airports.

Most of the price of that trip, and of a similarly extravagant jaunt to a conference in Prague, was business-class airfare. It now turns out, according to the Washington Examiner, that the fare covered not just the air travel of Mr. Martire but that of a female companion.

In response to news reports about Mr. Martire’s excesses and also to his conflict of interest in pushing pro-labor contracting rules for the Silver Line, Virginia Gov. Robert F. McDonnell (R) has tried to remove him from the board. Mr. Martire has refused to go. Instead, he has mounted a court challenge, forcing the authority to spend hundreds of thousands of dollars to defend his position.

True, the authority has no legal mechanism to fire Mr. Martire on its own. However, it can, and should, stop paying his spiraling legal bills.

For years the authority labored in dignified anonymity, free from controversy and the taint of politics. Predictably, scrutiny of its affairs intensified after it took over the $5.6 billion Silver Line, one of the nation’s biggest ongoing public infrastructure projects.

Now the Silver Line, nearly half finished, is at a critical juncture. Its financing is in doubt, and it needs to maintain political support to ensure completion. The authority can’t afford distractions and imbroglios like the one surrounding Mr. Martire, whose actions on the board have given rise to criticism from Transportation Secretary Ray LaHood and become fodder for Republicans in the U.S. Senate race underway in Virginia.

Mr. Martire must go. By remaining on the board — a symbol of excess and abuse — he subverts the Silver Line and politicizes the authority.