The laws regarding the use of tobacco, and the issues surrounding it, are continuing to change on all levels. The federal government has been involved since 1966, when the Surgeon General's health warnings were required on all cigarette packages. Warnings were required on all smokeless tobacco products beginning in 1987. Cigarette ads were banned from T-V and radio in 1971, and in 1993, the E-P-A officially declared secondhand smoke a known cancer-causer in humans. In 1998, the attorneys general of most states and the major United States tobacco companies agreed to settle more than 40 pending lawsuits brought by states against the tobacco industry. In exchange for dropping their lawsuits and agreeing not to sue in the future, the states received payments from the tobacco companies, and the companies were required to restrict their marketing activities and establish new efforts to curb tobacco consumption. Most states restrict or prohibit smoking in public places, forbid the sale of tobacco products to minors under age 18, as well as require I-D to purchase tobacco products. Some states and major cities have passed laws prohibiting smoking in bars and restaurants. Various individuals have attempted to take action in court against tobacco companies, with varying results. Smoking is banned by statute on almost all U-S domestic flights, and it's prohibited by international agreement on nonstop flights operated by U-S, Australian, Canadian, and New Zealand carriers among their territories. The vast majority of smoking bans on other international flights serving the United States are the result of voluntary action by airlines, with encouragement by the U-S Government.