For the last five years, satellite photos have shown continuing constructing of an underground bunker complex north of Damascus, Syria, This is believed to be the control center for the national air defense system. Progress has been slow because Syria is broke and unable to pay for the new missile systems that that the people in this underground complex would control.
Earlier this year, Russia suspended its program to upgrade Syria's MiG-31 fighters. In 2007, Russia and Syria signed an agreement by which Russia would provide the country with seven MiG-31 aircraft, as well as equipment and services to upgrade Syria's aging fleet of combat aircraft. The total value of the deal was estimated at $400-500 million. The problem, as usual, revolved around money. Syria simply does not have the cash to pay for the program. This is despite the fact that Russia forgave 70 percent of Syria's debt to them back in 2005. The Syrians had owed over $13 billion.
Syria has long been indebted to the Russians for years, much of it coming from arms and equipment purchased from the Soviet Union during the Cold War. During 1970s and '80s, Syria received large amounts of sophisticated weaponry from the Russians, and on excellent financial terms. This was due to the fact that the Soviets were more interested in maintaining political influence in the region and counterbalancing American influence. Obtaining and keeping allies was paramount. These days, making money is the number one priority for the Russians and the country needs customers who can actually pay. Also, Russia's interest in maintaining their sphere of influence is far less global than during the Cold War, with the Russian Federation almost entirely concerned with maintaining hegemony over the countries that border it. Preoccupied with their own defense reforms and the need to raise more cash quickly, the Russians simply can't afford to be as generous with giving away equipment as they used to be. Iran has been Syria's patron for over two decades, but has its own cash flow problems, which have resulted in Syria not being able to pay for several year old Russian arms deals.
Thus, the enormous expense involved in upgrading and obtaining even seven new combat aircraft would potentially take a crippling chunk out of Syria's already pitiful military budget, without a large "gift" from Iran. Syria can only afford to spend around a billion dollars, sometimes less, on its military annually and the since the deal demanded that the country pay out at least $400 million for the new planes and upgrades, this would potentially cut into the budget so much that it could even endanger the Syrian' ability to maintain any kind of forces at all, even if the money were paid out over a long period of time. The Syrians want to rebuild their armed forces back to the state they were during the 1973 and '82 wars with Israel, when they were largely equipped with up-to-date weapons and managed to maintain some professionalism. As it stands, the Syrians can barely afford to keep the equipment they do have running, much less pay out of pocket for new gear. The Syrians simply don't have the money and the Russians are less generous than in the past. So the new air-defense system is on hold.
Syria has put considerable effort into burying key defense assets. For example, Syria has underground storage and launch facilities for its arsenal of over a thousand SCUD missiles. North Korean and Iranian engineers have been seen in Syria for over a decade, apparently assisting in the construction of these underground facilities. The North Koreans expect to be paid, up front, in cash. But they are expert in the construction of underground bunkers.