BRUSSELS — Almost six years ago, the European Union sharply curtailed access to its airspace for Iran’s aging airline fleet. But officials in Brussels say they are now prepared to loosen some of those restrictions as the easing of Western sanctions gradually allows new planes and spare parts to enter Iran after decades of isolation.

The overture follows the nuclear accord reached with the United States and other world powers in January, and it will be presented during a visit to Tehran this weekend by a delegation from the European Commission, the bloc’s executive branch, officials said. It forms part of a broader European effort to revive economic ties between Iran and the 28-member bloc, which was once one of Iran’s largest trading partners.

Iranian state news media confirmed a visit this week by representatives of Boeing to discuss a possible sale of 737, 787 and 777 aircraft, the first such mission by the American plane maker in decades. The United States company’s European rival Airbus reached an agreement with Iran in January over the purchase of $27 billion in new jets.

The European Union banned most planes operated by Iran’s state-owned flag carrier, Iran Air, from its skies in 2010 because of concerns over their airworthiness. With an average age of more than 26 years, the airline’s fleet is one of the world’s oldest, and European and American trade restrictions had prohibited the sale of the spare parts needed to keep the planes properly maintained.