The no-fly zones are not patrolled 24 hours a day and never have been. The Iraqis are fully aware of this and make their fighter aircraft incursions when they know that their are no manned combat air patrols about. They have been doing this for years now and the numbers of Iraqi fighter aircraft incursions amount to the hundreds over the past couple of years alone.
A Pentagon briefing during 2000 highlighted the situation:
"The Pentagon said Thursday that six Iraqi aircraft violated that country’s southern no-fly zone Sept. 4 while allied aircraft took the day off, but officials refused to confirm reports that at least one Iraqi jet continued on to penetrate Saudi airspace.
Iraqi aircraft have violated the northern and southern no-fly zones more than 150 times since Operation Desert Fox in December 1998, the last major allied attack on Iraqi leader Saddam Hussein’s military forces, Pentagon spokesman Rear Adm. Craig Quigley said at a briefing Thursday.
Most of those violations have been quick, defiant dips into and out of the zones, established in the wake of the 1991 Persian Gulf War to constrain Iraqi military aggression in the region.
Quigley acknowledged that six Iraqi aircraft were involved in five separate violations of the southern zone on Sept. 4, flying "unequivocally south of 33 North," the latitude boundary line of that zone. He declined to be more specific.
But he admitted that Saddam’s air force has become adept at exploiting occasional gaps in allied air patrols over the zones.
The Iraqis were able to penetrate deeply into the southern no-fly zone and into Saudi Arabia last week because Saddam’s air-defense radar network, despite taking a near-constant battering from allied aircraft for almost a decade, apparently still is able to closely track those coalition air patrols.
"The Iraqi air-defense system clearly sees when the coalition is flying, and we were not flying that day," he said. "I can only assume that they felt this was an excellent opportunity to violate the southern no-fly zone. "Typically, the Iraqis do not fly when we are flying," he said. "They’re not looking for a fight with coalition aircraft. They have not put themselves into a position where coalition aircraft can engage them. They are looking only to try to reassert sovereignty over Iraqi airspace and, I guess, to show us that they still can." Coalition aircraft patrol the Iraqi zones "most of the time," Quigley said. "But we do have no-fly days, for a variety of reasons."
The United States has adopted a sort of rolling response policy to Saddam’s provocations in which attacks on various Iraqi military assets come "at a time and place, and in a manner, of our own choosing," Quigley said. Such attacks could be well-removed, both in time and distance, from the area where the Iraqi provocations originate and are not launched on a one-for-one basis. "We try not to keep a particular box score," he said. "It’s not necessarily tit for tat, or an immediate response."
Does this mean they might take out the planes on the ground at the airbase they flew from?