Dollar Thrifty Automotive Group ( DTG) was growing impatient with its suitors. The car rental holding company said Aug. 21 it sent a letter to Hertz Global ( HTZ) and Avis Budget ( CAR) asking them to submit their "best and final definitive proposals" on potential mergers by October. Dollar Thrifty CEO Scott Thompson said that continuing uncertainty over a transaction was in "no one's best interest." "Hertz and Avis have made substantial progress with respect to regulatory reviews, and our Board has concluded that the time has come to determine if, and on what terms, a transaction can be achieved," Thompson added. Hertz and Avis have been locked in a drawn-out bidding war over Dollar Thrifty.