A DC-10 jet airplane, designed and built by McDonnell (D) and operated by American (D) lost an engine and crashed in the immediate vicinity of the airport. All two hundred seventy-one persons aboard the plane, and two persons on the ground, were killed. There are one hundred eighteen wrongful death actions arising out of the crash. Many of the complaints allege wrongful death counts which request awards of punitive as well as compensatory damages. Ps and their decedents are residents of California, Connecticut, Hawaii, Illinois, Indiana, Massachusetts, Michigan, New Jersey, New York, Vermont, Puerto Rico, Japan, the Netherlands, and Saudi Arabia. McDonnell (D) is a Maryland corporation having its principal place of business, now and at the time of the accident, in Missouri. Ps contend McDonnell's (D) conduct in the design and manufacture of the DC-10 was egregious. They claim that misconduct occurred in California. American (D) is a Delaware corporation that had moved its prior place of business from New York to Texas. Ps contend that, on the date of the crash, American's (D) principal place of business was in Texas, but American (D) contends that its principal place of business on that date was New York. Ps contend that American's conduct regarding the maintenance of the DC-10 was egregious. That alleged misconduct occurred in Oklahoma, site of American's (D) maintenance base. Ds moved to strike the claims for punitive damages. Under dispute was whether certain states allowed punitive damages, the choice-of-law theories to be used regarding certain states, and the results of the application of the choice-of-law theories which were used. Using the choice-of-law rules of each state where these actions had originally been filed, the district court ruled as follows. Under the Illinois 'most significant relationship' test, the law of the state of the principal place of business should prevail with regard to the issue of punitive damages. Finding that New York was American's (D) principal place of business at the time of the crash and does not allow punitive damages and that Missouri, McDonnell's (D) does allow the equivalent of punitive damages, the court allowed the motions to strike punitive damage claims against American (D) but not McDonnell (D). Under the California 'comparative impairment' test, the policies of the state of the principal place of business would be impaired more than the policies of the state of misconduct if those policies were not applied. The court allowed the motion to strike punitive damage claims with regard to American (D) but not with regard to McDonnell (D). The district court reached the same result with regard to the actions filed in New York, Michigan, Puerto Rico, and Hawaii. Ps and McDonnell (D) appealed.