The Resolution Trust Corp. expects to take control of another 75 thrifts by the end of the first quarter of 1991, said David Cooke, the agency's executive director.

Pan Am said that United will honor up to $100 million of Pan Am tickets at face value in what Pan Am called the unlikely event that it stops flying. Pan Am completed the sale of its transatlantic routes to United in a $400 million package. United still faces opposition from competitors and British officials as it seeks to keep flying the old Pan Am routes into London's Heathrow Airport.

New York Telephone said more than 50 of its employees were fired, resigned or face pay cuts for accepting gifts from vendors. The employees were from the company's Buildings Department, which is responsible for construction and maintenance of company property.

MGM-Pathe Communications, the newly formed entertainment company, has fired about 300 employees, or nearly one-third of its work force, in the past week to cut costs.

American Airlines's Sabre computer reservation division is expected to announce a link with a consortium of European airlines, which has been attempting to build without success its own computer reservation network.

Housing starts for 1991 will fall 4.3 percent, the National Association of Home Builders predicted. The association said it expects the economy will slide into a "mild and brief" recession that will end about mid-1991.

Colman M. Mockler Jr., chairman of Gillette, and two other Gillette senior executives will retire, paving the way for a succession in leadership at the shaving products company. Mockler, 60, who has also been chief executive officer since 1975, will leave at the end of 1991.