It was the first time that a plane was downed since a ban on Iraqi flights south of the 32d parallel.
The area north of the parallel was barred to Iraqi flights to protect the Kurdish minority living there from aerial attacks.
At that point, they say, allied troops will not be able to remain on Iraqi territory or continue the ban on Iraqi flights over the area.
As many as 30,000 Kuwaitis were reported abducted during the Iraqi flight from Kuwait City, but officials now put the figure at 7,000.
By the time the ban on Iraqi flights took effect, shortly before sundown, many of the Independence's 70 planes were over southern Iraq.
The ban on Iraqi flights below the 32d parallel applies to both civilian air and military planes.
The Pentagon said on Thursday that there had not been any Iraqi civilian flights south of the 3nd parallel in the last month or so.
On Wednesday only two Iraqi flights, both by helicopters, were detected south of the 32d parallel.
Tension increased in May 1975 as Syria closed its airspace to Iraqi flights and both countries amassed troops on their borders.
Officials did not disclose the specific rules of engagement by which pilots will enforce the ban on Iraqi flights.