By Tim Hepher, Reuters | Jul. 25, 2014

U.S. planemaker Boeing has disclosed an agreement with Iran to provide airplane parts, relaxing a three-decade freeze in ties as part of a broader package of sanctions relief.

The agreement sets out general terms and conditions for the "potential sale of certain goods and services related to the safety of flight," Boeing said in a regulatory filing.

It marks the first acknowledged dealings between U.S. aerospace companies and Iran since the 1979 U.S. hostage crisis led to sanctions that deepened during the decade-old international dispute over Iran's nuclear program.

Boeing said its agreement with state carrier Iran Air covered airplane parts, manuals, drawings, service bulletins, navigation charts and data.

Boeing has also opened discussions with Iran Air Tours, a subsidiary of Iran Air, for similar goods and services, it said.

Iran agreed in November to curtail nuclear activities for six months from Jan. 20 in exchange for sanctions relief from Britain, China, France, Germany, Russia and the United States.

Iran and the six world powers this month agreed to a four-month extension of negotiations, diplomats close to the talks said.

The temporary window allows for the sale of parts to Iran Air, whose fleet includes vintage Boeing and Airbus jetliners delivered as long ago as 1978.

World powers meeting in Vienna had set a July 20 deadline to complete a long-term agreement that would resolve the dispute over Tehran's nuclear ambitions. But negotiators were unable to overcome differences on major sticking points and the deal was extended for four months last week.

Reuters reported in February that U.S. aerospace companies were seeking permission to sell airliner parts to Iran for the first time in three decades.

In April, Boeing and engine maker General Electric said they had received licenses from the U.S. Treasury Department to export spare parts

European planemaker Airbus reiterated on Thursday that it had applied for a U.S. export license but said it had not yet reached an agreement with Iran on how to implement it.

U.S. industry analysts say the sale of spare aircraft parts is seen as a diplomatic carrot for Iran, which for decades has relied on parts obtained on the black market or copied locally.

Middle East and aviation sources said the first deal between Boeing and Iran could benefit the U.S. company if a broader softening of sanctions is agreed.

Iran Air will initially need at least 100 jets if economic relations return to normal and will find it easier to do business with companies that co-operated during the current window for sanctions relief, the head of the airline told Reuters in an interview in June.

Iran estimates its eventual future need for aircraft at around 400 aircraft.