The move is part of a general drive by the Persian Gulf Arab states to bolster their military forces to counter Iran's growing arsenal of ballistic missiles.
Saudi Arabia and its partners on Iran's doorstep, along the western shore of the Persian Gulf, are far more vulnerable to attack than Israel, which is more distant and beyond the range of most of the strategic missiles Iran currently has deployed.
Kuwait, Qatar, Bahrain and the United Arab Emirates host U.S. military installations, which makes them a target for Iran if hostilities erupt.
Saudi Arabia, the United Arab Emirates and Kuwait are also leading oil producers, which makes them strategic targets for Iran.
The main weapon that the six member states of the Gulf Cooperation Council -- Saudi Arabia, the United Arab Emirates, Kuwait, Oman, Qatar and Bahrain -- have to strike the Iranians is their growing air power. Saudi Arabia and the Emirates in particular have potent air forces.
The Emirates, Kuwait, Qatar and Bahrain have U.S.-built Raytheon MIM-140F Patriot systems for defense against ballistic missiles.
The Emirates expects to finalize a deal with Lockheed Martin for the high-altitude THAAD system, including 147 missiles, in the next few months, Lockheed Martin officials say.
"Any war with Iran will be an air force and missile war, so Saudi Arabia has to enhance its air force's capabilities," Mustafa Alani of the Gulf Research Center in Dubai told Jane's Defense Weekly.
"Saudi procurement strategies have been focused on acquisition of the most advanced defense technologies so that they can be interoperable with (the United States) and (the F-15 upgrade) is the latest evidence of that."
Alani said that the Americans were allowing the Saudis to pay for the upgrade, transforming their F-15s into a "serious aircraft and not a symbolic one," with U.S. military grant funds because Washington didn't want to lose a lucrative market to the Europeans or the Russians.
The U.S. Goodrich Corp. said two weeks ago it had signed a deal with Saudi Arabia to upgrade its 154 F-15s, which include several variants, with Grid-Lock flight controls.
The retrofit of the aircrafts' ailerons, flaps, rudders and wingtips will put the Saudi jets on a par with U.S. Air Force F-15s, Goodrich said. Jane's reported that the upgrade deal was worth $50 million.
In May, the Saudi air force signed a $40 million contract with Lockheed Martin under the U.S. Foreign Military Sales program for Sniper Advanced Targeting Pods for its F-15S Eagle fighter bombers. That was the second such purchase since March 2009 and the pods greatly enhanced the F-15s' combat capabilities, U.S. military officials noted.
Not all the Saudis' 71 F-15S aircraft need these ground attack and reconnaissance pods at once, as some are used for bombing missions that don't require them.
The ATPs, which cost about $2 million apiece, contain forward-looking infrared radar for night operations and TV cameras that allow pilots flying at 20,000 feet to clearly see what is happening ahead of them.
The pods also contain laser designators for laser-guided precision bombs for use against such targets as missile launch sites and command-and-control bunkers.
In February, the Saudis signed a $1.9 billion deal to acquire the Storm Shadow cruise missile from France's MBDA as part of an upgrade package for their British-built 85 BAE Systems Tornado strike aircraft.
BAE, a major shareholder in the European missile producer, has delivered the first eight of 72 advanced Eurofighter Typhoon aircraft to the Saudi air force.
The Sunday Times of London reported June 12 that Saudi Arabia had agreed to allow Israeli warplanes to use its air space for any pre-emptive strike against Iran's nuclear installations. Riyadh, which would be inviting Iranian retaliation if it did that, has strongly denied that report.
The Media Line news service quoted Arie Egozi, aviation expert for Israel's top-selling newspaper Yediot Ahronot, as saying, "The Saudis are very worried about the growing power of Iran."
He said Saudi Arabia "is an air power which any country should take into account … The Saudis are investing all of their time in order to keep their capabilities high."
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