The Iranians know they are being watched by American spy satellites, and high flying recon aircraft (Global Hawk and U-2) as well. But they thought these spy-in-the-sky efforts would not get down the level of checking the loading of cargo aircraft. As a result of this particular incident, which was probably made public mainly to aggravate and annoy the Iranians, loading cargo will be a lot more complicated in the future. Weapons to be shipped by air will have to be loaded on trucks while under cover, and the truck itself will have to be covered in such a way that the identity of the weapon is not disclosed. Then the aircraft will also have to be loaded in such a way that overhead reconnaissance cannot observe what it going onto the aircraft.
Even that may not be enough, as nations, which Iranian transports normally fly over, may demand the right to inspect all cargo aircraft headed for Syria. The Israelis may even get involved, by announcing they will shoot down any Iranian heavy transports, suspected of carrying weapons for Hizbollah, that enter Syria. Israel is not happy with how so many countries just stood idly by while so many weapons were sent to Hizbollah. This time around, those shipments, or attempted shipments, won't be risk free.
The U.S. government has forced Iran to change the way it loads weapons in aircraft that are headed for Syria. American intelligence officials revealed how satellite reconnaissance had spotted Iranians loading eight C-802 anti-ship missiles, and three launchers into a Russian made Il-76 transport. This happened a day after a C-802 fired from the Lebanese coast had damaged an Israeli warship. Iraq refused to let the Iranian aircraft enter its air space. When the Iranian Il-76 headed for Turkey instead, the Turks said the Iranian aircraft could only transit Turkey if it first landed to see if it was carrying weapons in its cargo. The Il-76 declined and returned to an Iranian air base.