The US investment firm trying to buy easyJet has gone public with a £4.7bn takeover proposal for the budget airline, after three proposals were rebuffed by the easyJet board.

Castlelake said on Monday that an all-cash offer of 625p a share, valuing easyJet at just over £4.7bn, had been rejected on Sunday, after previous offers at 560p and 600p.

Castlelake said it had now decided to make the bid public so that easyJet shareholders could evaluate it before a takeover deadline on Friday.

“Castlelake expected that the third proposal would elicit prompt engagement from the easyJet board,” the company said. “Following the rejection of three proposals by the easyJet Board, and given its unwillingness to engage meaningfully, Castlelake is announcing this third proposal to enable easyJet shareholders to consider its merits and provide their views on the third proposal to the easyJet board.”

Under City takeover rules, Castlelake, which is headquartered in Minneapolis and manages $36bn (£27bn) in assets, has until 5pm on 26 June to announce whether it intends to make an offer for easyJet.

Castlelake also said it has partnered with two investors to meet EU regulations whereby European airlines must be majority owned by investors within the region. This rule still applies to easyJet, even after Brexit.

The company said it had partnered with Peter Bellew, a former chief operating officer at Riyadh Air, easyJet and Ryanair, and the former chief executive of Malaysia Airlines. Bellew currently runs Dooks Capital, a seed investment and advisory firm focused on AI in aviation, which he founded last September and operates out of Saudi Arabia.

The second partner is Mark Breen, chief executive of Dublin-based Oneiros Aerospace, whose previous experience includes working for Oman Air.

“The third proposal includes these EU national partners investing and participating in the proposed acquisition of the company through their ownership and control of an EU company,” said Castlelake. “This EU Partner will hold a controlling shareholding in the overall structure. The EU Partner will at all times be owned and controlled by EU nationals.

“This proposed structure is consistent with structures adopted by a number of other European airlines that are subject to the same EU ownership rules as the company. Castlelake is confident that this is a clear, deliverable solution to ensure compliance with all applicable regulatory requirements.”

Castlelake made its first approach earlier this month tabling a 403p a share bid valuing easyJet at £3bn.

At the time, easyJet hit out at its potential buyer saying it was “highly opportunistic timing”, as the airline’s share price was “temporarily depressed due to the current situation in the Middle East and its impact on customer confidence and jet fuel prices”.

Before news of takeover interest emerged, shares in easyJet had lost about a fifth of their value since the start of the year.

The airline’s share price has surged by 36% over the last month due to the prospects of a takeover. On Monday morning, the stock gained 2% to 515p.

In October, reports emerged that the Swiss-headquartered shipping company MSC was considering a takeover of the business. In 2021, easyJet rejected an approach from the rival airline Wizz Air.

EasyJet, which is headquartered in Luton and employs more than 16,000 people around the world, is one of Europe’s three biggest low-cost airlines, behind Ryanair, with Wizz Air in third place.

Castlelake is led by executive chair and founder Rory O’Neill and has assets under management worth $36bn. It entered talks in January with bankrupt US carrier Spirit Airlines over a possible takeover.

Castlelake previously bailed out collapsed Scandinavian Airlines (SAS) and then sold on its shares to Air France-KLM.