LONDON — When a technical error forced a Norwegian Air jet to land at Shiraz Airport in Iran last month, the Boeing 737 touched down in uncharted territory.

The airline, known for cheap long-haul flights from Europe, does not have a base in Iran. It had never flown there before. And nearly a month after it left Dubai, the brand-new American-made jet, delivered to Norwegian Air only in October, was still sitting in Shiraz.

The jet appeared to be caught up in United States sanctions on Tehran’s nuclear program that prohibit civilian aircraft sales, including services and parts. Those came into force again last year after President Trump withdrew from the 2015 nuclear deal that had eased punitive measures in return for verifiable pledges of peaceful nuclear work.

A technical error in one of the engines prompted the landing on Dec. 14, a spokesman for Norwegian Air said by phone on Tuesday, and the 186 passengers and six crew members on board were unharmed. They spent the night in Iran and flew to Oslo the next day.