A competing offer for control of National was submitted to the CAB by Pan Am, and National ultimately agreed to be acquired by Pan Am; these actions drove up the price of National's stock. The CAB gave TIA and Pan Am each permission to acquire up to 25% of National's shares, and the two companies acquired 45% of the shares in total. The management and directors of National, as a group, owned less than 5% of the outstanding shares. In December, Eastern Airlines also joined the bidding for National. TIA and Pan Am considered the bid a "ploy to block their own chances" of completing the deal, but Eastern chairman Frank Borman called the offer serious.