TEHRAN — Long before the first newly purchased Boeing airliner lands at Imam Khomeini International Airport, Iran and the United States will have had to come to terms with a new reality: American citizens will once again be taking up residence in Tehran, the first to do so since the Islamic Revolution and subsequent hostage crisis in 1979 and 1980.

When the United States on Wednesday gave the green light for the direct sale of Western planes to Iran, much more than nearly four decades of sanctions on such deals came to an end. Not that the deals approved by the Treasury Department are insignificant: 80 Boeing jets and an initial batch of 17 Airbus planes out of a potential total of 118.

But the sale will have the important effect of ending an era of absolute isolation between the countries. Boeing will almost certainly have to open an administrative office in Tehran, and technicians will have to move here to train their Iranian counterparts in the care and maintenance of the planes. Among them, almost certainly, will be many Americans.

That seems to be exactly what the United States had in mind in approving the deal, Iranian analysts say. The deal not only allows President Hassan Rouhani to show a tangible gain from warming relations with the West, but also moves Iran that much closer to his ultimate goal of normalization of relations with the United States.