ISS says new JetBlue offer more favorable for Spirit Airlines

June 28 (Reuters) - Institutional Shareholder Services (ISS) said JetBlue Airways Corp's latest offer to buy Spirit Airlines Inc is "more favorable" for the ultra-low-cost airline's shareholders, but maintained its support for the Frontier deal.

The influential proxy advisory firm in a report dated Monday said, with the shareholder meet to approve the deal set as early as Thursday, it was hesitant to change its earlier stand recommending them to vote for Frontier's offer.

Frontier's cash-and-stock offer was valued at $22.03 per share as of Monday's close, while JetBlue's offer, including a "ticking fee", was valued at $34.15 per share, a premium of 51% premium to Spirit's last close.

"The addition of the ticking fee in the JetBlue offer – a provision without a counterpart in the Frontier offer – provides a further level of regulatory risk mitigation," ISS said. (Reporting by Nathan Gomes in Bengaluru; Editing by Shinjini Ganguli)