FOUR YEARS AGO, an investigation by this newspaper found that members of the powerful governing board that controls publicly owned Dulles International and Reagan National airports, apparently mistaking themselves for oil sheiks or Hollywood moguls, had splurged on lavish meals and first-class trips to sumptuous destinations — sometimes with spouses — ostensibly to drum up business at industry conferences. In response, the board of the Metropolitan Washington Airports Authority pledged to tighten policies and practices, which were obviously lacking.

It would have been reasonable to expect energetic follow-up from the airports authority, especially given the intensifying scrutiny it faced as the agency in charge of building Metro’s $5.8 billion Silver Line extension to Dulles, one of the nation’s biggest infrastructure projects. Instead, the board, or at least some members, appears to have descended deeper into a pit of extravagant expenses, shady contracting and opaque procedures.

The latest alarming disclosures, contained in a report by the Transportation Department’s inspector general, amount to a case study in how not to cultivate trust with Congress, the public or the media. They contribute to a portrait of a governing board that is running amok — exactly the wrong message at a critical moment when the authority is trying to secure financing to complete the Silver Line.

Moreover, the ongoing federal investigation holds the distinct possibility of further damaging revelations to come — specifically pertaining to allegations of nepotism, which the inspector general’s report mentions but does not detail.

Incredibly, given the embarrassing exposéfour years ago, the inspector general found further examples of prolific spending on travel and entertainment. They included first-class air tickets to Hawaii and Florida; last-minute air fare of $9,200 paid for a trip to Prague; and a $4,800 tab from three dinners for unnamed board members and their unidentified guests, averaging $150 per person.

The public, which after all supports the authority’s $2 billion annual budget, deserves to know which board members were responsible for these slap-happy expenses.

Potentially more ominously, the inspector general’s report details a pattern of hundreds of millions of dollars in under-the-radar contracts handed out with scant regard for law, oversight or proper procedure. Although law requires the authority to seek competitive bids for contracts of more than $200,000 whenever possible, about two-thirds of almost 200 such contracts from 2009 to 2011 were not awarded in a full and open competition.

Although no evidence has been presented of sweetheart deals or conflicts of interest, the absence of proper control and procedures certainly deepens suspicions, which critics have already voiced.

On top of that, the report found that the authority’s governing board has displayed a fondness for secrecy that has been only partially addressed in response to the inspector general’s concerns. The inspector general said that the board’s policies on financial disclosure and transparency are insufficient and that it has had few independent audits since its creation 25 years ago.

It would be nice to think that the inspector general’s report will jolt the airports authority into long-overdue reforms and that the deficiencies already noted, as well as others that may be forthcoming, will not impede completion of the Silver Line. But recent history provides little comfort.