The European Union on Tuesday banned most of Iran Air’s jets from European airports, saying that the decision was based on safety concerns, and not because of the sanctions against Iran approved last month by the United Nations Security Council over its nuclear program.

After a safety audit, the union, a 27-nation bloc, decided to place Iran Air’s Boeing 727s and 747s, along with its Airbus 320s, on the organization’s blacklist, said a Transport Commission spokeswoman, Helen Kearns. The list consists of carriers that the union has determined do not meet international safety standards.

Ms. Kearns insisted that the move, which affects about two-thirds of Iran Air’s fleet, had nothing to do with international sanctions.

“We deal purely with safety requirements,” she said. “Our controls focus entirely on safety, nothing else.”

Iran Air has had trouble properly maintaining its aging Boeing jets, which were purchased in the 1970s, because of a 30-year-old United States ban on buying spare parts.

The airline, together with a cargo and a low-cost subsidiary, has more than 60 planes in its fleet. There are plans to replace older airliners with Russian-built Tu-204 medium-range jets starting next year.