design load factor compared to the F/A-18A's 7.5 g factor. The partnership between McDonnell Douglas and Northrop soured over competition for foreign sales for the two models. Northrop felt that McDonnell Douglas would put the F/A-18 in direct competition with the F-18L. In October 1979, Northrop filed a series of lawsuits charging that McDonnell was using Northrop technology developed for the F-18L for foreign sales of the F/A-18 in violation of their agreement, and asked for a moratorium on foreign sales of the Hornet. McDonnell Douglas countersued, alleging Northrop illegally used F/A-18 technology in its F-20 Tigershark. A settlement was announced 8 April 1985 for all of the lawsuits. McDonnell Douglas paid Northrop $50 million for "rights to sell the F/A-18 wherever it could". Additionally, the companies agreed on McDonnell Douglas as the prime contractor with Northrop as the principal subcontractor. As principal subcontractor, Northrop will produce the rear section for the F/A-18 (A/B/C/D/E/F), while McDonnell Douglas will produce the rest with final assembly to be performed by McDonnell Douglas. At the time of the settlement, Northrop had ceased work on the F-18L. Most export orders for the F-18L were captured by the F-16 or the F/A-18. The F-20 Tigershark did not enter production, and although the program was not officially terminated until 17 November 1986, it was dead by mid-1985. Into production During flight testing, the snag on the leading edge of the stabilators was filled in, and the gap between the leading-edge extensions (LEX) and the fuselage was mostly filled in. The gaps, called the boundary layer air discharge slots, controlled the vortices generated by the LEX and presented clean air to the vertical stabilizers at high angles of attack, but they also generated a great deal of parasitic drag, worsening the problem of the F/A-18's inadequate range. McDonnell filled in 80% of the gap, leaving a small slot to bleed air from the engine intake. This may have contributed to early problems with fatigue cracks appearing on the vertical stabilizers due to extreme structural loads, resulting in a short grounding in 1984 until the stabilizers were strengthened. Starting in May 1988, a small vertical fence was added to the top of each LEX to broaden the vortices and direct them away from the vertical stabilizers. This also provided a minor increase in controllability as a side effect. F/A-18s of early versions had a problem with insufficient rate