Israel striking Iran via Iraq with U.S. collusion is a moot point.
If Washington finds itself ready to use force against Tehran, it would be more politically expedient for the United States to attack Iran alone and avoid the political blowback of attacking a Muslim country jointly with Israel.
However, with more to lose if Iran becomes nuclear, Israel would have more incentive to strike than the United States would. In that case, the Israelis would be prepared to act unilaterally, without Washington's assistance — meaning without using Iraqi airspace — or perhaps even publicly admitted knowledge. However, if Washington or Israel should launch a strike against Iran, the two allies will coordinate with each other — probably behind the scenes.
In the event that Israel does decide to launch military strikes against Iranian nuclear facilities, IDF would have several options, including a nuclear strike using Jericho II missiles.
The most likely conventional option would be an Israeli Air Force (IAF) airstrike using F-15I Ra'am (Thunder) strike fighters from the 69th Squadron based at Hatzerim Air Base in the Northern Negev, about 50 miles south of Tel Aviv. The F-15I, similar to the U.S. Air Force's F-15E Strike Eagle, uses long-range technology with air superiority capabilities. Twenty-five F-15Is have been used in the IAF since 1999. Capable of carrying as much ordnance as a World War II heavy bomber, the F-15I can also deploy precision-guided munitions and can penetrate enemy air space at low levels and high speeds.
The IAF strike package will have to include other aircraft besides the F-15Is. Once they enter Iranian airspace, the Israelis will have to suppress Iranian air defenses. This would most likely be accomplished by F-16Is in the "Wild Weasel" role. On the way to the nuclear facilities, separate strike packages would have to neutralize the Iranian air force's (IRIAF) 3rd Tactical Air Base at Hamadan in order to prevent its F-4 fighters from interfering with the raid. On the way out, the IRIAF 2nd Tactical Air Base at Tabriz, with its F-5s and MiG-29s, would have to be neutralized. All of these strike aircraft — those sent against the nuclear facilities, the Wild Weasels and those sent against the Iranian air bases, would need their own fighter escorts as well.
Because the IAF routinely flies to Turkey to use the Anatolian bombing ranges, the movement of Israeli aircraft in that direction might not arouse much suspicion, depending on the level of tensions at the time. IAF refueling and surveillance aircraft, which would be required to support the strikes, can safely orbit inside Turkish airspace. In addition, any damaged IAF aircraft or shot down Israeli air crews would have a better chance of landing or surviving in Turkey or the Kurdish areas of Iraq than they would in Saudi Arabia, Syria or western Iraq.
At first glance, a sustained air campaign targeting Iran's nuclear program looks difficult for the IAF. However, Israel has shown itself to be very resourceful in the past when confronted with challenges. The main impediment to Israeli military action will be the difficulty of securing a route for the striking aircraft.