In April 1980, several U.S. aircraft penetrated Iran and landed on the desert mostly undetected, and what few witnesses there were, were detained.
Operation Eagle Claw
"
The plan was this:
"On the first night, six Air Force C-130s carrying 132 Delta commandos, Army Rangers, and support personnel and the helicopter fuel would fly from the island of Masirah, off the coast of Oman, more than 1,000 miles to Desert One, being refueled in flight from Air Force KC-135 tankers.
"Eight Navy RH-53Ds would lift off the aircraft carrier USS
Nimitz, about 50 miles south of the Iranian coast, and fly more than 600 miles to Desert One.
"After refueling, the helicopters would carry the rescue force to a hideout in hills about 50 miles southeast of Tehran, then fly to a separate hiding spot nearby. The C-130s would return to Masirah, being refueled in flight again."
Regarding "witnesses" during the mission:
"Soon after the first crews landed and began securing Desert One, a tanker truck, apparently smuggling fuel, was blown up nearby by the Delta Force roadblock team using a shoulder-fired rocket as it tried to escape the site. The truck's passenger was killed, but the driver managed to escape in an accompanying pickup truck. As the tanker truck was evaluated to be engaged in clandestine smuggling, the driver was not considered to pose a security threat to the mission... A civilian Iranian bus with a driver and 43 passengers traveling on the same road, which now served as the runway for the aircraft, was forced to halt at approximately the same time and the passengers were detained aboard Republic 3."
Equipment failure led to the mission being cancelled, and that was followed by a catastrophic collision which left many Americans dead. But until the collision, six C-130s and six American Sea Stallion helicopters went veritably undetected in the Iranian desert.
BTW, for the smart-asses that may wish to deprecate Wiki as a source, you can read Bowden's Guests of the Ayatollah: The Iran Hostage Crisis: The First Battle in America's War with Militant Islam on your nickel. It tells the same story.