UAL says that's the maximum amount that can be sold without jeopardizing the tax benefit the company is counting on to boost its financial recovery.
The move is the latest action in the legal battle over whether many or all employee-held shares in the ailing airline can be sold off.
The employee stock ownership plan was created in 1994 and has 75,000 members. Its trustee began selling 24 million shares in September, but was barred by temporary court order from selling off any more after the airline declared bankruptcy on Dec. 9.
United Airlines is the predominant carrier at Denver International Airport.