Washington Dulles International Airport is certainly taking its time to fully join the modern age of air travel, but the first steps in its journey are now complete, and they make an obvious difference. The most significant are the new international arrivals hall and the AeroTrain, which started running last week.

As readers of this column will recall, I have no love lost for Dulles. In the past, I’ve gone as far as to call it a disgrace for the capital of the world’s richest and most powerful country. Its many limitations include the archaic people-movers officially known as “mobile lounges” and the depressing interior of the “midfield terminal”…