Business Notes AIRLINES

When United Airlines paid $2.1 billion for new 747-300 and 747-400 jetliners from Seattle's Boeing last week, the No. 2 U.S. carrier secured more than standard safety equipment. As part of the deal, Boeing agreed to purchase $700 million in promissory notes convertible to stock in the airline's parent, Allegis, based in Elk Grove Village, Ill. If Boeing acquires stock, it could become the company's largest shareholder and thus help Allegis thwart hostile takeover attempts. Boeing cannot exceed a 30% share without the consent of Allegis' board.

The agreement did not quell speculative interest in Allegis stock, which rose 4 1/2 last week, closing at 72 3/8. Several unidentified investors were believed to be amassing large holdings. United's pilots union, which wants to buy the airline, said the Boeing-Allegis alliance will not affect its plans.