EasyJet has rejected a higher £4.93 billion approach from Castlelake but has extended the offer deadline to allow its US suitor more time to come up with a “more attractive proposal”.

The low cost carrier said Castlelake had submitted a fourth approach on Tuesday worth £6.50 a share. EasyJet said: “Having carefully reviewed it with its advisers, the board of easyJet continues to regard the fourth proposal as substantially undervaluing the company and its prospects and continuing to give rise to significant questions of deliverability.

“Accordingly, the board of easyJet has unanimously rejected the fourth proposal.

“However, the board believes that giving Castlelake access to limited commercial information, as Castlelake sought in the letter which contained the fourth proposal, might produce a more attractive proposal that better reflects the value of easyJet and its prospects and the interests of shareholders thereto.”

EasyJet added it “continues to be concerned about the ownership structure and deliverability of any offer from Castlelake”.

Earlier this week the budget carrier rejected another offer from Castlelake worth £4.74bn,accusing it of trying to buy the airline “on the cheap”.

Castlelake said it had made three further takeover approaches to the airline this month, all of which had been rejected.

The airline’s share price has risen by 40% over the past month amid prospects of a takeover. Shares were up 3.4% at 521p by early afternoon on Monday, making easyJet one of the top risers on the FTSE 250.

Founded by British‑Cypriot entrepreneur Stelios ⁠Haji‑Ioannou in 1995 EasyJet is one of Europe’s leading airlines. Last year they carried more than 90 million passengers with the airline operating across 38 countries on more than 1,200 routes.

EasyJet, which is headquartered in Luton, England, employs more than 16,000 people across the globe.

Castlelake, who already own a stake of about 2.14% in EasyJet through the funds it manages, previously bailed out collapsed Scandinavian Airlines before selling its shares to Air France-KLM.