easyJet has rejected a fourth takeover bid from US private credit group Castlelake valuing the airline at £4.9bn, but entered discussions after the suitor requested limited commercial information. The budget carrier said the 650p-a-share offer substantially undervalued the company and raised structural concerns about the potential deal. Shares jumped 5 percent to 566.6p on Thursday following the announcement.

Castlelake, which includes Brookfield as its parent group, told investors it hopes additional information will allow it to improve the offer. The firm is open to easyJet shareholders maintaining stakes in the airline and has structured the deal to meet EU ownership rules requiring at least 51 percent European control.

Several major shareholders told the Financial Times they would support engagement if the offer reaches £5.3bn or £7 per share. easyJet has asked the UK Takeover Panel to extend Castlelake's deadline from June 26 to July 5 to allow further negotiations.

The move signals easyJet's willingness to explore a deal while maintaining pressure on Castlelake to increase the price. Management's concerns about ownership structure and deliverability suggest the airline won't accept just any offer, even as it courts its largest investor.