VIRGINIA GOV. Robert F. McDonnell has become embroiled in a nasty, partisan-tinged fight, one that pits his administration against the authority that runs Dulles International and Reagan National airports. The stakes are high because the airports authority is also overseeing construction of Metro’s $6 billion Silver Line extension to Dulles, one of the nation’s biggest infrastructure projects. Last week the governor, a Republican, upped the ante by firing a Democratic appointee on the authority’s board of directors who also was its only union-affiliated member.

The object of Mr. McDonnell’s ire was Dennis L. Martire, a labor official who had more than two years left on his six-year board term. Mr. Martire, who was appointed by Mr. McDonnell’s Democratic predecessor, has shown bad judgment and a tin ear for public ethics. Whether his actions rise to a firing offense that stands up in court is another question.

As this page reported last month, Mr. Martire single-handedly ran up $38,000 in expenses attending five conferences in 2010 and 2011 — twice as much as the next most spendthrift board member. He used the airports authority’s funds to indulge a fondness for junkets, including one to the Mediterranean island of Sardinia, at a cost of more than $10,000, to attend a conference that had nothing to do with U.S. airports or aviation.

Most likely, though, the real deal-breaker for Mr. McDonnell was Mr. Martire’s advocacy of a union-friendly project labor agreement for the second phase of the Silver Line project. PLAs, as they’re known, are red flags for Virginia Republicans, even though they’re used for virtually every major state construction project. Mr. Martire, an official with the Laborers’ International Union of North America, should have had the common sense to avoid the appearance of a conflict of interest that his involvement created.

If common sense or ethical mindfulness were among the criteria for firing appointed board members, Mr. Martire’s dismissal would probably stick. But the legal authority for the governor’s action is much less apparent; it’s not clear whether Mr. Martire’s transgressions, though serious, are a sufficient basis for his firing. After all, the airports authority cleared his trips as well as his activism on the PLA question.

Mr. Martire filed a legal challenge to his dismissal almost immediately; at the moment, it’s not certain even whether the case will be resolved in federal or Virginia court, or how long it will take. On Monday, the airports authority asked a state court to settle the question of who should be seated on its board of directors, which meets Wednesday: Mr. Martire or Caren Merrick, a Republican businesswoman named as his replacement by Mr. McDonnell.

It would be nice if the mess could be settled with the wave of a wand or if Mr. Martire, whose poor judgment gave rise to the dispute, would resign. Nice, but unlikely.

What’s most important is that the clash not be allowed to disrupt or derail progress on the Silver Line, which is critical to Northern Virginia’s continued economic vitality. Whatever his misgivings about Mr. Martire or the airports authority, Mr. McDonnell needs to keep his focus on the goal — helping to secure financing and maintaining momentum to build a 21st-century transit link to the Washington region’s premier international airport.