By Greg Roumeliotis and Anirban Sen
NEW YORK (Reuters) -Frontier Group Holdings Inc has agreed to offer a break-up fee in a bid to secure its $2.9 billion acquisition of Spirit Airlines Inc, people familiar with the matter said on Thursday.
The sweetening of the terms comes after proxy advisory firm Institutional Shareholder Services Inc (ISS) urged Spirit shareholders to vote against the deal with Frontier, in part because Spirit failed to negotiate a break-up fee should U.S. antitrust regulators shoot down their deal.
JetBlue Airways Corp is trying to gatecrash the deal with a hostile $3.3 billion offer for Spirit that the latter has rejected, arguing regulators will not greenlight it unless JetBlue makes more concessions.
Frontier and Spirit may announce a revised deal that they hope will win support from Spirit shareholders as early as Thursday, the sources said, requesting anonymity because the matter is confidential. The size of the break-up fee could not be learned.
Spirit and Frontier did not immediately respond to requests for comment.
(Reporting by Greg Roumeliotis and Anirban Sen in New York; Editing by Chris Reese)
