The Federal Trade Commission soon will announce that the nation's three major aircraft manufacturers have agreed not to offer bribes and kickbacks to foster sales to foreign customers when competing with American companies.

The agreements are contained in similar consent orders signed by the Boeing Co., Lockheed Aircraft Corp., and McDonnell Douglas Corp., sources said yesterday.

The orders, which have been accepted on the provisional basis by the FTC, would settle proposed agency complaints that the companies had offered, and made, illegal payments in the past to influence the buying decisions of foreign governments and companies. In some instances, the payments effectively excluded other domestic aircraft manufacturers from selling their aircraft, aircraft parts and related services to the government or airlines whose officials, officers and employees who had received the payments, the FTC alleged.

The practice violates Section 5 of the Federal Trade Commission, which bars unfair practices, as well as the Robinson Patman Act, the FTC complaints charged.

The orders would prohibit each corporation, its officers, agents, employees, or representatives from offering to make or making payments to customers through any corporate or other device when the purpose is to have the customer favor the money-giver at the expense of one or more domestic - meaning U.S. - companies.

(A lawyer said the order would not appear to bar payments when the firm had no U.S. competition in a quest to make certain sales.)

Should one of the companies be found later to make an illegal payment under the order, a provision would require the payment of a civil penalty up to $10,000 per day for each day of the "continuing violation," from the date of any offering of payment or payment made until the date any contract procured by it was fulfilled or terminated.

The complaints to be made public by the FTC are said to be vague: they won't give names, dates, and amounts.But the orders are clearly tougher than the one Boeing signed last week to settle a Securities and Exchange Commission complaint. In that, Boeing agreed it would disclose any payments it makes to its stockholders.

The orders also go beyond a law signed last year that bars bribes to foreign officials by barring illegal payments to all entities, government or not, a source said.