United’s pilots vowed to press their bid for airline.

The United Airlines Pilots Assn. said it would continue its effort to buy the carrier, despite the rejection of its $4.5-billion offer. The board of Chicago-based UAL Inc., which owns the airline, rejected the offer as “grossly inadequate” Friday. In a statement, the union called the rejection inexcusable, irresponsible and a disservice to shareholders. “The pilots are committed to this transaction. Accordingly, we will consider and pursue alternative courses of action to achieve the employee purchase of the airline.” A union spokesman declined to outline any of these alternatives.