Other bases remain secret. Besides Saudi Arabia, another exists in Oman, possibly on Masirah island, while the US plans to expand its North Africa reach with a base in Niger or Burkina Faso. Drones can be launched from US Navy vessels or military bases.
As with nuclear bombs in 1945 the US dominates UAV technology. They are relatively cheap, unmanned, and able to stay aloft for long periods and pinpoint targets (although, controversially, not without civilian casualties).
While much attention is paid to US drone strikes in the Middle East and North Africa, less is paid to drones operated by other states - and what might happen if their use conflicts with US interests.
Take the Asia-Pacific region, where the US has been redeploying military assets since the Bush Administration, shifting more nuclear ballistic submarines and carrier fleets from the Atlantic as part of a military, political and economic "pivot" announced in President Barack Obama's first term.
According to Peter Singer, director of the Brookings Institution's 21st Century Defence Initiative, 76 nations are "now building, buying or using drones, including all the key powers in Asia. China and Japan, for example, both have programmes to use UAVs for surveillance and patrols over disputed islands".
Certainly, China is building its UAV fleet as the US beds in its Asia-Pacific pivot. Last August, Chinese defence experts reportedly visited Iran to inspect a captured RQ-170 Sentinel, a US stealth drone allegedly shot down in 2011. The US currently flies Global Hawk spy drones from Guam and plans to deploy a fleet of MQ-4C Triton drones, able to provide continuous "broad area" maritime surveillance, in 2013.
Meanwhile, rising Sino-Japanese tensions over the Senkaku Islands (known as the Diaoyu in China) in the East China Sea - along with disputes between Vietnam, Indonesia, Malaysia and the Philippines over ownership of other small island groups above oil resources in the South China Sea - have seen growing UAV deployment.
Last August, then US Defence Secretary Leon Panetta, in a Pentagon meeting with Japanese Defence Minister Satoshi Morimoto, said US drones would survey the Senkakus. Japan, more bearish on defence since conservatives took office in December, is buying Global Hawks.
China unveiled eight new drone models in November (many resemble US aircraft, like the Global Hawk and the armed Predator and Reaper), sparking fears of an arms race where Beijing can outspend Washington. Despite fears spending on drones may give China the edge in future regional disputes, the US still leads in technological sophistication.
However, any race underlines the need for a legal framework when using military UAVs; how would the US react if China - or India or Russia - had a "kill list" of enemies?
The US commitment to Japan is underwritten by a defence treaty. It is a scenario, the first time rival drones are known to have been used in a regional dispute [excepting Israel and Hizbollah over Gaza], which heightens the potential for incidents.
"Yes. That's indisputable, I think," says Ron Huisken, an East Asia security expert with the Australian National University.
"But as long as everyone is gathering intelligence then probably the net effect is a good one. It gives decision makers on the mainland almost as good a picture of what's happening around the Senkakus as navy captains. Who may be a bit hot-headed. So, it's not an unmitigated disaster."
While a clash between naval vessels or military planes might spiral out of control, sabre-rattling with drones sends a message without immediately threatening life.
Given China's fears the pivot is really Cold war-style containment this is just as well, even as US drones signal Washington has a stake in the region. "America never left," says Huisken. "But the perception grew [among allies and rivals] that the region was nowhere near the top of anyone's in-tray in Washington for a long time."
The Senkaku dispute with a key American ally suggests China may have underestimated US commitment, assuming Washington had been laid low by 9/11, the Iraq war and the global economic slowdown, suggests Huisken. But the US can still project daunting firepower - far more than Beijing despite efforts to build up its military.
As the Sino-Japanese dispute deepens and tensions soar in the Korean Peninsula, following Pyongyang's third nuclear bomb test and the launch of a ballistic rocket last December, the appearance of US drones above the Senkakus is a clear indication the US intends to remain a player in a region it regards as strategically important.
