easyJet shares jumped on Monday after the airline agreed in principle to Castlelake’s £6.90-a-share cash proposal, valuing the carrier at £5.2 billion, or up to £5.5 billion on a fully diluted basis. The stock rose about 11%, helping lift European travel shares, but remained well below the offer price, signaling investor doubts over whether the deal can overcome U.K. and European airline ownership rules, regulatory hurdles and execution risks. The companies extended the deadline for a firm offer to Aug. 3 at 5 p.m. London time and said there is no certainty a binding bid will emerge.